From patchwork Wed Oct 9 18:07:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829001 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 748501E049A; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; cv=none; b=Q3JT+SU02L7V0NJOIQaZBy1Wz+RNTlFZZe16RltMSMNX/xTvpAav0TSw0AFG02rLjBhKfxREn/j4FE3YUxesoF5uibHyEn3ZEIY0qG10ax5CYTo8quSxMk0wpQg7GdzFiKw/C3ug1awo1EA2bzlKsaJbLxjPHS+aKH5HolT/MMI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; c=relaxed/simple; bh=YtrJn4vc+Mgz9wgw7+EugcgaEZCddJzBtXAuSeGGRxU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Fk0RXcNnr1hf07NQDbapjfUh2o2PgMfQPRIiQDE1fHhC198Ld6qJ9EqOB7QKqjRMzL2gXD0CEtgV1QwONYQq2k5fv3x8R7ZYLapfsgPccBAfRJyLf81kGxUzNvVk+KR8YCpbvl7Lxt88LsjcMmkh4/MHPRiI+qI5nLH2x1aSV7Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ET1UOC2l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ET1UOC2l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4FBD9C4CEC3; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=YtrJn4vc+Mgz9wgw7+EugcgaEZCddJzBtXAuSeGGRxU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ET1UOC2lI3v1Dq1UGsIUa/wz6CxnBK0fLf+88jg3nMdROL9RjWii/LfE0MVDpOtsU 8YqrAUdUogXgllkIIZdxN/UNCE8G2VEtWjOxNAw+v5Q++kUrb8xUNcm5U/SoTQPrkv CfD4SydBPN8otoyPqEPkv4SVHS+6RIGdXa/YMpi92aR4InHtuUSBl8o6b31bRu5CkJ 7Hn2ld5c5JwfM+KfZFnotvxQdOLJwAp2rOH6hqiw4RZVBwBB+2cjQJn20pfUZPY9ql S6CV6f81tnS/rT9gr02xy1vplk5KRbmUgHOjRSIQwEHgB2Kuwp3QtFOsuCMpmqZMec ZwbJQz0NrCEpQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 0EFF7CE08E5; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 01/12] srcu: Rename srcu_might_be_idle() to srcu_should_expedite() Date: Wed, 9 Oct 2024 11:07:08 -0700 Message-Id: <20241009180719.778285-1-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 SRCU auto-expedites grace periods that follow a sufficiently long idle period, and the srcu_might_be_idle() function is used to make this decision. However, the upcoming light-weight SRCU readers will not do auto-expediting because doing so would cause the grace-period machinery to invoke synchronize_rcu_expedited() twice, with IPIs all around. However, software-engineering considerations force this determination to remain in srcu_might_be_idle(). This commit therefore changes the name of srcu_might_be_idle() to srcu_should_expedite(), thus moving from what it currently does to why it does it, this latter being more future-proof. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: Reviewed-by: Neeraj Upadhyay --- kernel/rcu/srcutree.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 31706e3293bce..9ff4ded609ba5 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1139,7 +1139,8 @@ static void srcu_flip(struct srcu_struct *ssp) } /* - * If SRCU is likely idle, return true, otherwise return false. + * If SRCU is likely idle, in other words, the next SRCU grace period + * should be expedited, return true, otherwise return false. * * Note that it is OK for several current from-idle requests for a new * grace period from idle to specify expediting because they will all end @@ -1159,7 +1160,7 @@ static void srcu_flip(struct srcu_struct *ssp) * negligible when amortized over that time period, and the extra latency * of a needlessly non-expedited grace period is similarly negligible. */ -static bool srcu_might_be_idle(struct srcu_struct *ssp) +static bool srcu_should_expedite(struct srcu_struct *ssp) { unsigned long curseq; unsigned long flags; @@ -1469,14 +1470,15 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); * Implementation of these memory-ordering guarantees is similar to * that of synchronize_rcu(). * - * If SRCU is likely idle, expedite the first request. This semantic - * was provided by Classic SRCU, and is relied upon by its users, so TREE - * SRCU must also provide it. Note that detecting idleness is heuristic - * and subject to both false positives and negatives. + * If SRCU is likely idle as determined by srcu_should_expedite(), + * expedite the first request. This semantic was provided by Classic SRCU, + * and is relied upon by its users, so TREE SRCU must also provide it. + * Note that detecting idleness is heuristic and subject to both false + * positives and negatives. */ void synchronize_srcu(struct srcu_struct *ssp) { - if (srcu_might_be_idle(ssp) || rcu_gp_is_expedited()) + if (srcu_should_expedite(ssp) || rcu_gp_is_expedited()) synchronize_srcu_expedited(ssp); else __synchronize_srcu(ssp, true); From patchwork Wed Oct 9 18:07:09 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829005 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C54A71E1A17; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; cv=none; b=d8H4oSnFFHWUp+4XXFaKjth7RPAjndCBq0Rfe/T5pzwU7lt4eccPnaBtJKVWt8hch/KJd/XB8tguEgqdpYMYSfYvTWB4rmnmK56rkIls/ffY1xA9BcnWADIvouw9wJwIG56W0tEHBTy4rrv555rEf7n4vDmn4SkmT5su5UeBSYI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; c=relaxed/simple; bh=wmL8nD35K+D183HPbTxmWpox+7fCqVw7eRDQh/aakYc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ZkmrwZVzXMHBOW5J/bYW6BFjFa5t4GlNV2pSHAxKB70Hyrq7VWhphW2HZH1Ud+fXYIrbfIV/NFv3Bq5Kt0s3QjgGwBK6TWZ6CxQF2MGPMVJIh69VK2fR0eWgLJot84P+BrXoZIbFZ9ULO7z3bPIyZBCAktxkVKWNKddZCyo5WFw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZtHyMAzi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZtHyMAzi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F0ADC4CECC; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=wmL8nD35K+D183HPbTxmWpox+7fCqVw7eRDQh/aakYc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZtHyMAzi5pzVy2FO6NdbHf1NjpkLld39dm+aDhUmCMhDih/CCOF+vcj1qNUlAzVo3 xzXk7hkxptMPUO5Vc4t5wsewui8Asg2VYaVHbgjmTGIFo21rY9g0Ne9o94tm3N/Vme LNlMYqjC57KmIhE93FHAFTiEXXrkHZofwQg8WwL9JRw4yuOv64sdlRXgt+eHE5ZMQM flCE8cJE3SG0LKmBI5MR0zMDMchsgvPqltBhy7Ist8vZqvPHA0pwHEraTjLbzWc+y2 Vhk0GMe4zwynZfTAO85mD9DulKtNzWXiA3Rt19UDSR/INKkd8fZLYPtvr/MS5eXhAW 9WvJ/OS5cqAwA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 12413CE0B68; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 02/12] srcu: Introduce srcu_gp_is_expedited() helper function Date: Wed, 9 Oct 2024 11:07:09 -0700 Message-Id: <20241009180719.778285-2-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Even though the open-coded expressions usually fit on one line, this commit replaces them with a call to a new srcu_gp_is_expedited() helper function in order to improve readability. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: Reviewed-by: Neeraj Upadhyay --- kernel/rcu/srcutree.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 9ff4ded609ba5..e29c6cbffbcb0 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -418,6 +418,16 @@ static void check_init_srcu_struct(struct srcu_struct *ssp) spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags); } +/* + * Is the current or any upcoming grace period to be expedited? + */ +static bool srcu_gp_is_expedited(struct srcu_struct *ssp) +{ + struct srcu_usage *sup = ssp->srcu_sup; + + return ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp)); +} + /* * Returns approximate total of the readers' ->srcu_lock_count[] values * for the rank of per-CPU counters specified by idx. @@ -622,7 +632,7 @@ static unsigned long srcu_get_delay(struct srcu_struct *ssp) unsigned long jbase = SRCU_INTERVAL; struct srcu_usage *sup = ssp->srcu_sup; - if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp))) + if (srcu_gp_is_expedited(ssp)) jbase = 0; if (rcu_seq_state(READ_ONCE(sup->srcu_gp_seq))) { j = jiffies - 1; @@ -867,7 +877,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) spin_lock_irq_rcu_node(sup); idx = rcu_seq_state(sup->srcu_gp_seq); WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); - if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_needed_exp))) + if (srcu_gp_is_expedited(ssp)) cbdelay = 0; WRITE_ONCE(sup->srcu_last_gp_end, ktime_get_mono_fast_ns()); From patchwork Wed Oct 9 18:07:10 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829004 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C54471E1A16; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; cv=none; b=JbFWFJAQxbOcAsncxPnL6Z85iGhe86Vpb/pYvjOwC/CmximE+xhROF6HHPMokEhYFMRgzQ4xCt3jRaDCJ0O/J3bvfR9fgMFgsLruSJdk/xksSOOQIPsVLpbAbZ4aIqmn8DWtdhT+XXZ/fkVPmBj740McqOhodKnAjK4D57O2zBM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; c=relaxed/simple; bh=Zx5VaivUvDu8VT1tnLqC/VtTV/C14Gn+/PcOHscidtA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=C5t7q9XTLzPMhkCf/fbhEqW5WMRPW5fG98RTYfKPGNQwC9r8bFvX2vS4nO3W2ylIw5kUBAEkDN9NeFsyMYxQXkT/yCJtRCx4jphQpgCetTmMUvMD9Gst6IynbtLp3w0f+70W5h3ciOayN1PESDVOwsi0F0QrPZm7dyYLG/4J6YM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oVxpN3Ox; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oVxpN3Ox" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DD01C4AF0D; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=Zx5VaivUvDu8VT1tnLqC/VtTV/C14Gn+/PcOHscidtA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oVxpN3Oxt7MZHy2pIUddMKwaIsF9KkfyYu9iV3VFdo2v46VNeIbHSBuWvTy8NJP0p IzLXl5eGvNE5k8vir5aGQMdQ22HnZKCn0ASWwLV9hC5oAxm6GCfQFAEbFx0p0vkfS6 XjI14t3HsCia6NRnyFNZk15f0VGPhNIsHoNFgJrNJbWJsW25zqBC9xpn2sb5pdk1J3 YWt3uFAiLUbP785/9ZueUZNIwI8f5wMF6L1g5ONLRxpKKq6o0aXWe6B4YqkXsf5oA/ uZvXDmGWoyMiarxnZd7+fEXyK2Kav3hhDQE01e8Rwa1yXwI0F0Uxtu2CdibenPmmHr /BkG844QD5Jtw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 154CBCE0BB1; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 03/12] srcu: Renaming in preparation for additional reader flavor Date: Wed, 9 Oct 2024 11:07:10 -0700 Message-Id: <20241009180719.778285-3-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Currently, there are only two flavors of readers, normal and NMI-safe. A number of fields, functions, and types reflect this restriction. This renaming-only commit prepares for the addition of light-weight (as in memory-barrier-free) readers. OK, OK, there is also a drive-by white-space fixeup! Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcu.h | 21 ++++++++++----------- include/linux/srcutree.h | 2 +- kernel/rcu/srcutree.c | 22 +++++++++++----------- 3 files changed, 22 insertions(+), 23 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 835bbb2d1f88a..06728ef6f32a4 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -181,10 +181,9 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) #define SRCU_NMI_SAFE 0x2 #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) -void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); +void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); #else -static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, - bool nmi_safe) { } +static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { } #endif @@ -245,7 +244,7 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) { int retval; - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); retval = __srcu_read_lock(ssp); srcu_lock_acquire(&ssp->dep_map); return retval; @@ -262,7 +261,7 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp { int retval; - srcu_check_nmi_safety(ssp, true); + srcu_check_read_flavor(ssp, true); retval = __srcu_read_lock_nmisafe(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; @@ -274,7 +273,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) { int retval; - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); retval = __srcu_read_lock(ssp); return retval; } @@ -303,7 +302,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) { WARN_ON_ONCE(in_nmi()); - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); return __srcu_read_lock(ssp); } @@ -318,7 +317,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); srcu_lock_release(&ssp->dep_map); __srcu_read_unlock(ssp, idx); } @@ -334,7 +333,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_nmi_safety(ssp, true); + srcu_check_read_flavor(ssp, true); rcu_lock_release(&ssp->dep_map); __srcu_read_unlock_nmisafe(ssp, idx); } @@ -343,7 +342,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) static inline notrace void srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) { - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); __srcu_read_unlock(ssp, idx); } @@ -360,7 +359,7 @@ static inline void srcu_up_read(struct srcu_struct *ssp, int idx) { WARN_ON_ONCE(idx & ~0x1); WARN_ON_ONCE(in_nmi()); - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); __srcu_read_unlock(ssp, idx); } diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index ed57598394de3..ab7d8d215b84b 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -25,7 +25,7 @@ struct srcu_data { /* Read-side state. */ atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */ atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */ - int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */ + int srcu_reader_flavor; /* Reader flavor for srcu_struct structure? */ /* Update-side state. */ spinlock_t __private lock ____cacheline_internodealigned_in_smp; diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index e29c6cbffbcb0..18f2eae5e14bd 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -460,7 +460,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) sum += atomic_long_read(&cpuc->srcu_unlock_count[idx]); if (IS_ENABLED(CONFIG_PROVE_RCU)) - mask = mask | READ_ONCE(cpuc->srcu_nmi_safety); + mask = mask | READ_ONCE(cpuc->srcu_reader_flavor); } WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask >> 1)), "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); @@ -699,25 +699,25 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); #ifdef CONFIG_PROVE_RCU /* - * Check for consistent NMI safety. + * Check for consistent reader flavor. */ -void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe) +void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { - int nmi_safe_mask = 1 << nmi_safe; - int old_nmi_safe_mask; + int reader_flavor_mask = 1 << read_flavor; + int old_reader_flavor_mask; struct srcu_data *sdp; /* NMI-unsafe use in NMI is a bad sign */ - WARN_ON_ONCE(!nmi_safe && in_nmi()); + WARN_ON_ONCE(!read_flavor && in_nmi()); sdp = raw_cpu_ptr(ssp->sda); - old_nmi_safe_mask = READ_ONCE(sdp->srcu_nmi_safety); - if (!old_nmi_safe_mask) { - WRITE_ONCE(sdp->srcu_nmi_safety, nmi_safe_mask); + old_reader_flavor_mask = READ_ONCE(sdp->srcu_reader_flavor); + if (!old_reader_flavor_mask) { + WRITE_ONCE(sdp->srcu_reader_flavor, reader_flavor_mask); return; } - WARN_ONCE(old_nmi_safe_mask != nmi_safe_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_nmi_safe_mask, nmi_safe_mask); + WARN_ONCE(old_reader_flavor_mask != reader_flavor_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask); } -EXPORT_SYMBOL_GPL(srcu_check_nmi_safety); +EXPORT_SYMBOL_GPL(srcu_check_read_flavor); #endif /* CONFIG_PROVE_RCU */ /* From patchwork Wed Oct 9 18:07:11 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829003 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C53F21E1A15; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; cv=none; b=L12yV3O9MCcw4Dv7QM9ufwJbW0iTSlTtHUwmAMJ3TGuvJeh7dws5JkQS02ETl4SjAxDDaB8RJme+7AX/JWQJyJFT1BksZvZ7SQqHj2ey7YZCP/ZkBKsjsFBPO7pK3PXjcITo6lJkU1jaFBvgZZrEgsEO6IrxcrB9tTIy3L2uJIE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; c=relaxed/simple; bh=HtkA9wBw7Sojuw5HhHk7JjMMtDq6tne9Y9iMOe1hFF4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=hl2OwjL3sW9sLD6nA9983XK6/2RKKNk8c2vL4QU4tHEjs1cx6vyaYEX2oML14uNo7SHozHKvDMrwF/kC9R5QcjPifzhIwVDPwVc3s7mH3sgwc0JutuUmzHJev7sHkDn71eLerv7boy+HmxNl3aGDOeT6fGjsErz2rxB8PmQemjc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eqGPF8Aq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eqGPF8Aq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F304C4CED1; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=HtkA9wBw7Sojuw5HhHk7JjMMtDq6tne9Y9iMOe1hFF4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eqGPF8AqxWt/aL5IflAfoA230W+8o//V+Z2zhRDAQwwntw3FvlmAPKdZYgZZdZIGi khwys5GRAwatZlqCM82NEqUK457Sb2erAn7DxBcV686NpjeqghOj2h8e1zqR7OjJIl C64pLzxzeJ5kJgB2BICFQ8QcFIFf7X4rcNkHDo0WsPob6eyNO/oo25Tw+tB+aootXF NcDxrrSkIBv2qTyQ3UfQQCoBg91oo+E8d1e9SqD4alLOM1ZDZ842/nBcTpSyArb0RF f2FlBveOvWqjtqLcGJaYCnbqF/XbJIvdgAGiG/331fFV07qClA/7egqhTqNXbjzkt/ 7bXgVlw42rwXA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 18532CE0DD1; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 04/12] srcu: Bit manipulation changes for additional reader flavor Date: Wed, 9 Oct 2024 11:07:11 -0700 Message-Id: <20241009180719.778285-4-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Currently, there are only two flavors of readers, normal and NMI-safe. Very straightforward state updates suffice to check for erroneous mixing of reader flavors on a given srcu_struct structure. This commit upgrades the checking in preparation for the addition of light-weight (as in memory-barrier-free) readers. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/srcutree.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 18f2eae5e14bd..abe55777c4335 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -462,7 +462,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) if (IS_ENABLED(CONFIG_PROVE_RCU)) mask = mask | READ_ONCE(cpuc->srcu_reader_flavor); } - WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask >> 1)), + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); return sum; } @@ -712,8 +712,9 @@ void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) sdp = raw_cpu_ptr(ssp->sda); old_reader_flavor_mask = READ_ONCE(sdp->srcu_reader_flavor); if (!old_reader_flavor_mask) { - WRITE_ONCE(sdp->srcu_reader_flavor, reader_flavor_mask); - return; + old_reader_flavor_mask = cmpxchg(&sdp->srcu_reader_flavor, 0, reader_flavor_mask); + if (!old_reader_flavor_mask) + return; } WARN_ONCE(old_reader_flavor_mask != reader_flavor_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask); } From patchwork Wed Oct 9 18:07:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829002 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C53911E1A14; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; cv=none; b=ClbQWrXztiAMobGWyWs4EsLaRPiP7NQh+uQR7TyavcFhwgOXRgWHgeojalE9MLXtKbvwg0cawvDAbIOsEbARbfzeG1sHlilJy+GU1wxd9apfMO9PynbQky0nJTv7t97hQLhcE6UbFo2dpybEitDFwd65VgfUeaUhxwSSYlibeD4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497241; c=relaxed/simple; bh=6e6nFQakYcsfA7al8QMxHMj/HwDI3C+Crb6uuY7zJh4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=t6bbV+jkhAfG4IsJJJPuwYNxcsZFGXugXHO6jDqGU+tjal0fMn2fPAhn4Y+vpqiTwb4fGaOyxk2SSntHuWftGMqE6jafMXEl2X7Ovk0Lgx4ms++4hBnmwmshZS9AykcZocKdu9g3Gbbjy8OaAfKWurTfF+4Umm041eTKVZ5np14= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DjCWTyyl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DjCWTyyl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85C5EC4CED6; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=6e6nFQakYcsfA7al8QMxHMj/HwDI3C+Crb6uuY7zJh4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DjCWTyyl2rmeqnUqffPXoqUq+s5+PO2rZaFqk41vooX4AHsh6JEiVmiJK5tLJmE3d pZnVXwc29TH7YIZSBSUlrB7thxtC7rK9PBVggwHB8nqwlHNh5rUrAFKnlVZSjo4Sof +cUYBUfVkoMHKBeofoSwAtiWhcB8QMcOkajMsPWVrL8Kmiyl//I+Qyj/aadWSZRsQd Jh+7bbvdEAhW5EP1YLDwdbdIdxXxxhHVeVRapYU6nZCkHK1m5cPqLlrAa7F/c/rAPb SZF2z6AxTJIhGCq4Ae73bMOl1OCcMedcirmRKm6+B13vw40B6FS9SypQ5yADEIqLzp EVKN1zv97Qopw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 1BC03CE0E61; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 05/12] srcu: Standardize srcu_data pointers to "sdp" and similar Date: Wed, 9 Oct 2024 11:07:12 -0700 Message-Id: <20241009180719.778285-5-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit changes a few "cpuc" variables to "sdp" to align wiht usage elsewhere. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcu.h | 35 ++++++++++++++++++---------------- include/linux/srcutree.h | 4 ++++ kernel/rcu/srcutree.c | 41 ++++++++++++++++++++-------------------- 3 files changed, 44 insertions(+), 36 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 06728ef6f32a4..84daaa33ea0ab 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -176,10 +176,6 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -#define SRCU_NMI_UNKNOWN 0x0 -#define SRCU_NMI_UNSAFE 0x1 -#define SRCU_NMI_SAFE 0x2 - #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); #else @@ -235,16 +231,19 @@ static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flav * a mutex that is held elsewhere while calling synchronize_srcu() or * synchronize_srcu_expedited(). * - * Note that srcu_read_lock() and the matching srcu_read_unlock() must - * occur in the same context, for example, it is illegal to invoke - * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() - * was invoked in process context. + * The return value from srcu_read_lock() must be passed unaltered + * to the matching srcu_read_unlock(). Note that srcu_read_lock() and + * the matching srcu_read_unlock() must occur in the same context, for + * example, it is illegal to invoke srcu_read_unlock() in an irq handler + * if the matching srcu_read_lock() was invoked in process context. Or, + * for that matter to invoke srcu_read_unlock() from one task and the + * matching srcu_read_lock() from another. */ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) { int retval; - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); retval = __srcu_read_lock(ssp); srcu_lock_acquire(&ssp->dep_map); return retval; @@ -256,12 +255,16 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) * * Enter an SRCU read-side critical section, but in an NMI-safe manner. * See srcu_read_lock() for more information. + * + * If srcu_read_lock_nmisafe() is ever used on an srcu_struct structure, + * then none of the other flavors may be used, whether before, during, + * or after. */ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) { int retval; - srcu_check_read_flavor(ssp, true); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); retval = __srcu_read_lock_nmisafe(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; @@ -273,7 +276,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) { int retval; - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); retval = __srcu_read_lock(ssp); return retval; } @@ -302,7 +305,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) { WARN_ON_ONCE(in_nmi()); - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); return __srcu_read_lock(ssp); } @@ -317,7 +320,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); srcu_lock_release(&ssp->dep_map); __srcu_read_unlock(ssp, idx); } @@ -333,7 +336,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_read_flavor(ssp, true); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); rcu_lock_release(&ssp->dep_map); __srcu_read_unlock_nmisafe(ssp, idx); } @@ -342,7 +345,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) static inline notrace void srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) { - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); __srcu_read_unlock(ssp, idx); } @@ -359,7 +362,7 @@ static inline void srcu_up_read(struct srcu_struct *ssp, int idx) { WARN_ON_ONCE(idx & ~0x1); WARN_ON_ONCE(in_nmi()); - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); __srcu_read_unlock(ssp, idx); } diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index ab7d8d215b84b..79ad809c7f035 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -43,6 +43,10 @@ struct srcu_data { struct srcu_struct *ssp; }; +/* Values for ->srcu_reader_flavor. */ +#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). +#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). + /* * Node in SRCU combining tree, similar in function to rcu_data. */ diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index abe55777c4335..4c51be484b48a 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -438,9 +438,9 @@ static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx) unsigned long sum = 0; for_each_possible_cpu(cpu) { - struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); - sum += atomic_long_read(&cpuc->srcu_lock_count[idx]); + sum += atomic_long_read(&sdp->srcu_lock_count[idx]); } return sum; } @@ -456,14 +456,14 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) unsigned long sum = 0; for_each_possible_cpu(cpu) { - struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); - sum += atomic_long_read(&cpuc->srcu_unlock_count[idx]); + sum += atomic_long_read(&sdp->srcu_unlock_count[idx]); if (IS_ENABLED(CONFIG_PROVE_RCU)) - mask = mask | READ_ONCE(cpuc->srcu_reader_flavor); + mask = mask | READ_ONCE(sdp->srcu_reader_flavor); } WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), - "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); + "Mixed reader flavors for srcu_struct at %ps.\n", ssp); return sum; } @@ -564,12 +564,12 @@ static bool srcu_readers_active(struct srcu_struct *ssp) unsigned long sum = 0; for_each_possible_cpu(cpu) { - struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu); + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); - sum += atomic_long_read(&cpuc->srcu_lock_count[0]); - sum += atomic_long_read(&cpuc->srcu_lock_count[1]); - sum -= atomic_long_read(&cpuc->srcu_unlock_count[0]); - sum -= atomic_long_read(&cpuc->srcu_unlock_count[1]); + sum += atomic_long_read(&sdp->srcu_lock_count[0]); + sum += atomic_long_read(&sdp->srcu_lock_count[1]); + sum -= atomic_long_read(&sdp->srcu_unlock_count[0]); + sum -= atomic_long_read(&sdp->srcu_unlock_count[1]); } return sum; } @@ -703,20 +703,21 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); */ void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { - int reader_flavor_mask = 1 << read_flavor; - int old_reader_flavor_mask; + int old_read_flavor; struct srcu_data *sdp; - /* NMI-unsafe use in NMI is a bad sign */ - WARN_ON_ONCE(!read_flavor && in_nmi()); + /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor values. */ + WARN_ON_ONCE((read_flavor != SRCU_READ_FLAVOR_NMI) && in_nmi()); + WARN_ON_ONCE(read_flavor & (read_flavor - 1)); + sdp = raw_cpu_ptr(ssp->sda); - old_reader_flavor_mask = READ_ONCE(sdp->srcu_reader_flavor); - if (!old_reader_flavor_mask) { - old_reader_flavor_mask = cmpxchg(&sdp->srcu_reader_flavor, 0, reader_flavor_mask); - if (!old_reader_flavor_mask) + old_read_flavor = READ_ONCE(sdp->srcu_reader_flavor); + if (!old_read_flavor) { + old_read_flavor = cmpxchg(&sdp->srcu_reader_flavor, 0, read_flavor); + if (!old_read_flavor) return; } - WARN_ONCE(old_reader_flavor_mask != reader_flavor_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask); + WARN_ONCE(old_read_flavor != read_flavor, "CPU %d old state %d new state %d\n", sdp->cpu, old_read_flavor, read_flavor); } EXPORT_SYMBOL_GPL(srcu_check_read_flavor); #endif /* CONFIG_PROVE_RCU */ From patchwork Wed Oct 9 18:07:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829008 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 036FE1E1A3F; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=EOBamJi7KgYUqifJNvMbphOSeu2bGhMdbp9LOVjZmTx9vP6GVvZ5ivslBxN8tGMnZwCHs5pjdYuC+IC/n/FTqhSH3DEA7kR78Dq+zI2JylUKKz5+kmJdOHyqF8Pe1mXat/t3o/FLYXXrD02BVC3tngobv/Ajkm7aoZYMHMJah8s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=LFRisZMxRbIMr0KIalT12nZOMI5l1WeI4c/6S81vXZY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=tqbik1QcAE3fl2/rvNzBzuenfL0V/vTZJo4E5D2jNqyHBUBRAIXsL60bpOmMN7+XZ+yKmLbKiWOApZxKP6As2GKC8WDRrj0ECeQaunKTzvZSdqsvMwMqqsfTA0q26QN/GBTT/L0mdd942r4PPG8cCKGL3XoKg4sPyvGu5bwnies= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Y6PLiV5h; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y6PLiV5h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8E8BC4CEDB; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=LFRisZMxRbIMr0KIalT12nZOMI5l1WeI4c/6S81vXZY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y6PLiV5hCQ3Bs54YutxKqK+xlsInTTEcjEkPSXlGQ5oHFxBg/Jd6Dgb7ulSrN/uUX stvEO0q98b6WOVaQ7EwBxJGqnJxkfnwS5HOqbRuxgDsI+uUgNchQz8hrPjYtKvg0NV ohZiVYoEe/QP1uRfwG05Maip1bwbJ0Fpm3vleCMjaXegF9b18xieql8C9jVbJUzfFM /ktcYHJ3h0xzWhtcMRuEjdKYza9qr8O5QdvMQ22YN2Fe4OZbzEyExrjFk5a1iu+oFR 4a/iQ0SVvezfRMvFIPRTaUXA89ldWf87G5z+P3hUdYi6KFxC6Y/zZ5V9opNyYwwlP+ j2Me4z8iPSGkg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 1F4D4CE10CB; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , kernel test robot , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 06/12] srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite() Date: Wed, 9 Oct 2024 11:07:13 -0700 Message-Id: <20241009180719.778285-6-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This patch adds srcu_read_lock_lite() and srcu_read_unlock_lite(), which dispense with the read-side smp_mb() but also are restricted to code regions that RCU is watching. If a given srcu_struct structure uses srcu_read_lock_lite() and srcu_read_unlock_lite(), it is not permitted to use any other SRCU read-side marker, before, during, or after. Another price of light-weight readers is heavier weight grace periods. Such readers mean that SRCU grace periods on srcu_struct structures used by light-weight readers will incur at least two calls to synchronize_rcu(). In addition, normal SRCU grace periods for light-weight-reader srcu_struct structures never auto-expedite. Note that expedited SRCU grace periods for light-weight-reader srcu_struct structures still invoke synchronize_rcu(), not synchronize_srcu_expedited(). Something about wishing to keep the IPIs down to a dull roar. The srcu_read_lock_lite() and srcu_read_unlock_lite() functions may not (repeat, *not*) be used from NMI handlers, but if this is needed, an additional flavor of SRCU reader can be added by some future commit. [ paulmck: Apply Alexei Starovoitov expediting feedback. ] [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Paul E. McKenney Tested-by: kernel test robot Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcu.h | 51 ++++++++++++++++++++++++- include/linux/srcutree.h | 1 + kernel/rcu/srcutree.c | 82 ++++++++++++++++++++++++++++++++++------ 3 files changed, 122 insertions(+), 12 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 84daaa33ea0ab..4ba96e2cfa405 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -56,6 +56,13 @@ void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, void cleanup_srcu_struct(struct srcu_struct *ssp); int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); +#ifdef CONFIG_TINY_SRCU +#define __srcu_read_lock_lite __srcu_read_lock +#define __srcu_read_unlock_lite __srcu_read_unlock +#else // #ifdef CONFIG_TINY_SRCU +int __srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(ssp); +void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) __releases(ssp); +#endif // #else // #ifdef CONFIG_TINY_SRCU void synchronize_srcu(struct srcu_struct *ssp); #define SRCU_GET_STATE_COMPLETED 0x1 @@ -179,7 +186,7 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); #else -static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { } +#define srcu_check_read_flavor(ssp, read_flavor) do { } while (0) #endif @@ -249,6 +256,32 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) return retval; } +/** + * srcu_read_lock_lite - register a new reader for an SRCU-protected structure. + * @ssp: srcu_struct in which to register the new reader. + * + * Enter an SRCU read-side critical section, but for a light-weight + * smp_mb()-free reader. See srcu_read_lock() for more information. + * + * If srcu_read_lock_lite() is ever used on an srcu_struct structure, + * then none of the other flavors may be used, whether before, during, + * or after. Note that grace-period auto-expediting is disabled for _lite + * srcu_struct structures because auto-expedited grace periods invoke + * synchronize_rcu_expedited(), IPIs and all. + * + * Note that srcu_read_lock_lite() can be invoked only from those contexts + * where RCU is watching. Otherwise, lockdep will complain. + */ +static inline int srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(ssp) +{ + int retval; + + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE); + retval = __srcu_read_lock_lite(ssp); + rcu_try_lock_acquire(&ssp->dep_map); + return retval; +} + /** * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. * @ssp: srcu_struct in which to register the new reader. @@ -325,6 +358,22 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) __srcu_read_unlock(ssp, idx); } +/** + * srcu_read_unlock_lite - unregister a old reader from an SRCU-protected structure. + * @ssp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * Exit a light-weight SRCU read-side critical section. + */ +static inline void srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) + __releases(ssp) +{ + WARN_ON_ONCE(idx & ~0x1); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE); + srcu_lock_release(&ssp->dep_map); + __srcu_read_unlock(ssp, idx); +} + /** * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. * @ssp: srcu_struct in which to unregister the old reader. diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 79ad809c7f035..8074138cbd624 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -46,6 +46,7 @@ struct srcu_data { /* Values for ->srcu_reader_flavor. */ #define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). #define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). +#define SRCU_READ_FLAVOR_LITE 0x4 // srcu_read_lock_lite(). /* * Node in SRCU combining tree, similar in function to rcu_data. diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 4c51be484b48a..bf51758cf4a64 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -429,20 +429,29 @@ static bool srcu_gp_is_expedited(struct srcu_struct *ssp) } /* - * Returns approximate total of the readers' ->srcu_lock_count[] values - * for the rank of per-CPU counters specified by idx. + * Computes approximate total of the readers' ->srcu_lock_count[] values + * for the rank of per-CPU counters specified by idx, and returns true if + * the caller did the proper barrier (gp), and if the count of the locks + * matches that of the unlocks passed in. */ -static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx) +static bool srcu_readers_lock_idx(struct srcu_struct *ssp, int idx, bool gp, unsigned long unlocks) { int cpu; + unsigned long mask = 0; unsigned long sum = 0; for_each_possible_cpu(cpu) { struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); sum += atomic_long_read(&sdp->srcu_lock_count[idx]); + if (IS_ENABLED(CONFIG_PROVE_RCU)) + mask = mask | READ_ONCE(sdp->srcu_reader_flavor); } - return sum; + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), + "Mixed reader flavors for srcu_struct at %ps.\n", ssp); + if (mask & SRCU_READ_FLAVOR_LITE && !gp) + return false; + return sum == unlocks; } /* @@ -473,6 +482,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) */ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) { + bool did_gp = !!(raw_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE); unsigned long unlocks; unlocks = srcu_readers_unlock_idx(ssp, idx); @@ -482,13 +492,16 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) * unlock is counted. Needs to be a smp_mb() as the read side may * contain a read from a variable that is written to before the * synchronize_srcu() in the write side. In this case smp_mb()s - * A and B act like the store buffering pattern. + * A and B (or X and Y) act like the store buffering pattern. * - * This smp_mb() also pairs with smp_mb() C to prevent accesses - * after the synchronize_srcu() from being executed before the - * grace period ends. + * This smp_mb() also pairs with smp_mb() C (or, in the case of X, + * Z) to prevent accesses after the synchronize_srcu() from being + * executed before the grace period ends. */ - smp_mb(); /* A */ + if (!did_gp) + smp_mb(); /* A */ + else + synchronize_rcu(); /* X */ /* * If the locks are the same as the unlocks, then there must have @@ -546,7 +559,7 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) * which are unlikely to be configured with an address space fully * populated with memory, at least not anytime soon. */ - return srcu_readers_lock_idx(ssp, idx) == unlocks; + return srcu_readers_lock_idx(ssp, idx, did_gp, unlocks); } /** @@ -750,6 +763,47 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int idx) } EXPORT_SYMBOL_GPL(__srcu_read_unlock); +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Returns an index that must be passed to the matching + * srcu_read_unlock_lite(). + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +int __srcu_read_lock_lite(struct srcu_struct *ssp) +{ + int idx; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite()."); + idx = READ_ONCE(ssp->srcu_idx) & 0x1; + this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ + barrier(); /* Avoid leaking the critical section. */ + return idx; +} +EXPORT_SYMBOL_GPL(__srcu_read_lock_lite); + +/* + * Removes the count for the old reader from the appropriate + * per-CPU element of the srcu_struct. Note that this may well be a + * different CPU than that which was incremented by the corresponding + * srcu_read_lock_lite(), but it must be within the same task. + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) +{ + barrier(); /* Avoid leaking the critical section. */ + this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter); /* Z */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite()."); +} +EXPORT_SYMBOL_GPL(__srcu_read_unlock_lite); + #ifdef CONFIG_NEED_SRCU_NMI_SAFE /* @@ -1134,6 +1188,8 @@ static void srcu_flip(struct srcu_struct *ssp) * it stays until either (1) Compilers learn about this sort of * control dependency or (2) Some production workload running on * a production system is unduly delayed by this slowpath smp_mb(). + * Except for _lite() readers, where it is inoperative, which + * means that it is a good thing that it is redundant. */ smp_mb(); /* E */ /* Pairs with B and C. */ @@ -1152,7 +1208,8 @@ static void srcu_flip(struct srcu_struct *ssp) /* * If SRCU is likely idle, in other words, the next SRCU grace period - * should be expedited, return true, otherwise return false. + * should be expedited, return true, otherwise return false. Except that + * in the presence of _lite() readers, always return false. * * Note that it is OK for several current from-idle requests for a new * grace period from idle to specify expediting because they will all end @@ -1181,6 +1238,9 @@ static bool srcu_should_expedite(struct srcu_struct *ssp) unsigned long tlast; check_init_srcu_struct(ssp); + /* If _lite() readers, don't do unsolicited expediting. */ + if (this_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE) + return false; /* If the local srcu_data structure has callbacks, not idle. */ sdp = raw_cpu_ptr(ssp->sda); spin_lock_irqsave_rcu_node(sdp, flags); From patchwork Wed Oct 9 18:07:14 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829009 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 072771E1C02; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=L1DG9dR3YqW3blgB1XsaBe+mUmCLyNgWXdH1/QqE+pOoog7sYselOlHyBvNp28XnqpeHXe2ArhrdAKJV+sVe14B0PqI1hiiWq3Is+F/1gXQCXLvjyiZU5/8BJ54pHPkvXpPu8abowtlYglrdChLLjvQ16W4mpJ+uO8+8fwFR8G8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=ZPs4GAsD/9UDFSL0kqRU9kqwjKToL5QXnB6ewDSvNoI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Jpzn8IFRK3pMlndKhUxx6l6zGSwLiBA4/IBLxNmER4FVcWviOpxAnDN4S/XhpmtgOPYhIMw4FKnDqTlTy/AgT+e5EHnIQUl4XokrDb099/fGgrINLcuma1O/ncd/tAI0J28s9oThEcFO0DKuHcuXLKOJp6PrB39IO2oTjIJFzJY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=O0PHNFAD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="O0PHNFAD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B268AC4CEDE; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=ZPs4GAsD/9UDFSL0kqRU9kqwjKToL5QXnB6ewDSvNoI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O0PHNFAD30Vf0GtpziQkbT9V9kbWCV/Pm6iDB8LyJUhk5yug8KqhOwfUJpYfU0mFG 3u4Mr1yfMxbsM10ICDiYWz0oVUdMjrzEHtr7R0d2AfapucNLGuyqVrbjrGVnisbd7/ gWiga5taEVwu+xKk9QOOd5njsfnVrF7TD69fE6jYMzaW+O7KlFVKG63tUfVv7tQGqU oFwrsjJ9kfduCXuKN0J7RUXIsFUaACuXhEjkYdd+e7h/Vm+arYByvhST6B9qiQRked uP3H4Bu9BUMvn4hKKG/EnelrSZoczEUPX2/eUanCVKVcnkCp9UbtFDGPv3fUQQaTXp f+7G2+qEVf2Tw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 22B5DCE1290; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 07/12] srcu: Allow inlining of __srcu_read_{,un}lock_lite() Date: Wed, 9 Oct 2024 11:07:14 -0700 Message-Id: <20241009180719.778285-7-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit moves __srcu_read_lock_lite() and __srcu_read_unlock_lite() into include/linux/srcu.h and marks them "static inline" so that they can be inlined into srcu_read_lock_lite() and srcu_read_unlock_lite(), respectively. They are not hand-inlined due to Tree SRCU and Tiny SRCU having different implementations. Reported-by: Alexei Starovoitov Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcutree.h | 39 ++++++++++++++++++++++++++++++++++++++ kernel/rcu/srcutree.c | 41 ---------------------------------------- 2 files changed, 39 insertions(+), 41 deletions(-) diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 8074138cbd624..778eb61542e18 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -209,4 +209,43 @@ void synchronize_srcu_expedited(struct srcu_struct *ssp); void srcu_barrier(struct srcu_struct *ssp); void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Returns an index that must be passed to the matching + * srcu_read_unlock_lite(). + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +static inline int __srcu_read_lock_lite(struct srcu_struct *ssp) +{ + int idx; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite()."); + idx = READ_ONCE(ssp->srcu_idx) & 0x1; + this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ + barrier(); /* Avoid leaking the critical section. */ + return idx; +} + +/* + * Removes the count for the old reader from the appropriate + * per-CPU element of the srcu_struct. Note that this may well be a + * different CPU than that which was incremented by the corresponding + * srcu_read_lock_lite(), but it must be within the same task. + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) +{ + barrier(); /* Avoid leaking the critical section. */ + this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter); /* Z */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite()."); +} + #endif diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index bf51758cf4a64..07147efcb64d3 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -763,47 +763,6 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int idx) } EXPORT_SYMBOL_GPL(__srcu_read_unlock); -/* - * Counts the new reader in the appropriate per-CPU element of the - * srcu_struct. Returns an index that must be passed to the matching - * srcu_read_unlock_lite(). - * - * Note that this_cpu_inc() is an RCU read-side critical section either - * because it disables interrupts, because it is a single instruction, - * or because it is a read-modify-write atomic operation, depending on - * the whims of the architecture. - */ -int __srcu_read_lock_lite(struct srcu_struct *ssp) -{ - int idx; - - RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite()."); - idx = READ_ONCE(ssp->srcu_idx) & 0x1; - this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ - barrier(); /* Avoid leaking the critical section. */ - return idx; -} -EXPORT_SYMBOL_GPL(__srcu_read_lock_lite); - -/* - * Removes the count for the old reader from the appropriate - * per-CPU element of the srcu_struct. Note that this may well be a - * different CPU than that which was incremented by the corresponding - * srcu_read_lock_lite(), but it must be within the same task. - * - * Note that this_cpu_inc() is an RCU read-side critical section either - * because it disables interrupts, because it is a single instruction, - * or because it is a read-modify-write atomic operation, depending on - * the whims of the architecture. - */ -void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) -{ - barrier(); /* Avoid leaking the critical section. */ - this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter); /* Z */ - RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite()."); -} -EXPORT_SYMBOL_GPL(__srcu_read_unlock_lite); - #ifdef CONFIG_NEED_SRCU_NMI_SAFE /* From patchwork Wed Oct 9 18:07:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829007 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 003F01E1A37; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=ZnEMCcdXPFvQqTxvZwjh/7MFDT3GX2qQiVbGtZAgcTllaNb+nZIMij5SzJ2sc3Q0+RIiwdccCs83+pblkKvNHEocTS478fcgHIJKd63szlSR61jVGOUTLZGAF+hZqBM8EzxSKeCpvi/pR+wFuGVmLpSTGWy8x3iey7pqtPA230U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=8hfp/Du5Ub9QEkjtr1jYWVVr4ZGe06rAIhqfw3Hf/sc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Nu80CVzE/3SljmBgDKnEya0Tk4EllFEf+IP4KC49849IaTh9yBAxZ3DNgm7yMsvetxLBcUdqivF6DSMlIjOGIfnnMe++W7aaSYRpvvGXuwjQ28z4D9+DoMXF+TDGQw8YlB021HAbbwHNQb8GYnyg97zxEGEF+w7L50PI12vc640= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R2Bove1C; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R2Bove1C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B19A6C4CEDD; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=8hfp/Du5Ub9QEkjtr1jYWVVr4ZGe06rAIhqfw3Hf/sc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R2Bove1CxN9O3t+3f4epgXH9FlAwJt8guCyG6qgqYxPERi41AXQBBh+Ft1HLNTZWD 8MJnaZxUFg8QQLp0Oqn6fIYPOLx5UwBy4+/Om4arXhBvr6AVyovGdRbKqCskD8w6l6 zZmLF2HYjoKcZs7ZBLFQMG+RRqvAHBkka1P3ZAyGzwZ/WGTNZRrDyIfMO1also+gT3 /Yk28W/gPyOqFy+jihd8Fuga+wGGUGMAJ5CWVmook/48oivGDvcua/JbR41q22x3ln ol/MNPxE2Xa3MG/SPPIqNeqtweZDUjsAuTc8EDMeOhfYeUvmtka2N62sWMKXoL5qoz CzWrqIjecIPSw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 260C3CE1291; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 08/12] rcutorture: Expand RCUTORTURE_RDR_MASK_[12] to eight bits Date: Wed, 9 Oct 2024 11:07:15 -0700 Message-Id: <20241009180719.778285-8-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit prepares for testing of multiple SRCU reader flavors by expanding RCUTORTURE_RDR_MASK_1 and RCUTORTURE_RDR_MASK_2 from a single bit to eight bits, allowing them to accommodate the return values from multiple calls to srcu_read_lock*(). This will in turn permit better testing coverage for these SRCU reader flavors, including testing of the diagnostics for inproper use of mixed reader flavors. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/rcutorture.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 3ac8c69dd5bc9..ea71a23b45d8b 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -57,9 +57,9 @@ MODULE_AUTHOR("Paul E. McKenney and Josh Triplett extendables field, extendables param, and related definitions. */ #define RCUTORTURE_RDR_SHIFT_1 8 /* Put SRCU index in upper bits. */ -#define RCUTORTURE_RDR_MASK_1 (1 << RCUTORTURE_RDR_SHIFT_1) -#define RCUTORTURE_RDR_SHIFT_2 9 /* Put SRCU index in upper bits. */ -#define RCUTORTURE_RDR_MASK_2 (1 << RCUTORTURE_RDR_SHIFT_2) +#define RCUTORTURE_RDR_MASK_1 (0xff << RCUTORTURE_RDR_SHIFT_1) +#define RCUTORTURE_RDR_SHIFT_2 16 /* Put SRCU index in upper bits. */ +#define RCUTORTURE_RDR_MASK_2 (0xff << RCUTORTURE_RDR_SHIFT_2) #define RCUTORTURE_RDR_BH 0x01 /* Extend readers by disabling bh. */ #define RCUTORTURE_RDR_IRQ 0x02 /* ... disabling interrupts. */ #define RCUTORTURE_RDR_PREEMPT 0x04 /* ... disabling preemption. */ @@ -71,6 +71,9 @@ MODULE_AUTHOR("Paul E. McKenney and Josh Triplett > RCUTORTURE_RDR_SHIFT_2) > 1); + WARN_ON_ONCE(idxold2 & ~RCUTORTURE_RDR_ALLBITS); rtrsp->rt_readstate = newstate; /* First, put new protection in place to avoid critical-section gap. */ @@ -1850,9 +1853,9 @@ static void rcutorture_one_extend(int *readstate, int newstate, if (statesnew & RCUTORTURE_RDR_SCHED) rcu_read_lock_sched(); if (statesnew & RCUTORTURE_RDR_RCU_1) - idxnew1 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1; + idxnew1 = (cur_ops->readlock() << RCUTORTURE_RDR_SHIFT_1) & RCUTORTURE_RDR_MASK_1; if (statesnew & RCUTORTURE_RDR_RCU_2) - idxnew2 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2; + idxnew2 = (cur_ops->readlock() << RCUTORTURE_RDR_SHIFT_2) & RCUTORTURE_RDR_MASK_2; /* * Next, remove old protection, in decreasing order of strength @@ -1872,7 +1875,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, if (statesold & RCUTORTURE_RDR_RBH) rcu_read_unlock_bh(); if (statesold & RCUTORTURE_RDR_RCU_2) { - cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1); + cur_ops->readunlock((idxold2 & RCUTORTURE_RDR_MASK_2) >> RCUTORTURE_RDR_SHIFT_2); WARN_ON_ONCE(idxnew2 != -1); idxold2 = 0; } @@ -1882,7 +1885,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, lockit = !cur_ops->no_pi_lock && !statesnew && !(torture_random(trsp) & 0xffff); if (lockit) raw_spin_lock_irqsave(¤t->pi_lock, flags); - cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1); + cur_ops->readunlock((idxold1 & RCUTORTURE_RDR_MASK_1) >> RCUTORTURE_RDR_SHIFT_1); WARN_ON_ONCE(idxnew1 != -1); idxold1 = 0; if (lockit) @@ -1897,16 +1900,13 @@ static void rcutorture_one_extend(int *readstate, int newstate, if (idxnew1 == -1) idxnew1 = idxold1 & RCUTORTURE_RDR_MASK_1; WARN_ON_ONCE(idxnew1 < 0); - if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1)) - pr_info("Unexpected idxnew1 value of %#x\n", idxnew1); if (idxnew2 == -1) idxnew2 = idxold2 & RCUTORTURE_RDR_MASK_2; WARN_ON_ONCE(idxnew2 < 0); - WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1); *readstate = idxnew1 | idxnew2 | newstate; WARN_ON_ONCE(*readstate < 0); - if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1)) - pr_info("Unexpected idxnew2 value of %#x\n", idxnew2); + if (WARN_ON_ONCE(*readstate & ~RCUTORTURE_RDR_ALLBITS)) + pr_info("Unexpected readstate value of %#x\n", *readstate); } /* Return the biggest extendables mask given current RCU and boot parameters. */ @@ -1931,7 +1931,7 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ; unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH; - WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1); + WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1); // Can't have reader idx bits. /* Mostly only one bit (need preemption!), sometimes lots of bits. */ if (!(randmask1 & 0x7)) mask = mask & randmask2; From patchwork Wed Oct 9 18:07:16 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829010 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 088CD1E1C06; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=shN8k6ZFxGfqq7cBdTRUowp9nz2d/Kc1pgpKlOrSV/Cr9rQIGD05g+EoXOudnaWwm9OFG/VjYQdJHUYyuFgDziGusH5P4AZpcT0/xYVqQBBDercECZ4kLs8huUisIxEU8wBvUXt9iahpT/L7QOQCHfjDnTSabwSAK/8xmTQ1KGg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=fJSvDPbs5qEe3xzeWqWg6cC0gjZ2F5XS48/PJ5m/X38=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=DppF1/R3wd7nVk5cTtcA44SIMC/Z+R+3j0WATyW+wtZDgFbznooZXWsLxrLvwD2FeCulURM3mVPMP/3Rv0dC0/hTLnbI2IuchEZ1nn1TuXFDeeTpX61TomrnwEzTkm0mBXJ3TdwD/zl0zGWrSeVzQM3tKVATHZi/Iu+6PpNNlUc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iIebKXLR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iIebKXLR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2F9BC4CEE2; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=fJSvDPbs5qEe3xzeWqWg6cC0gjZ2F5XS48/PJ5m/X38=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iIebKXLRBvuGkKsUXQp3OUpXr4QkO4OifoHojg5c6FpRqIe8J+1Cm3ubv3rMhbh2B 3RileIR4LzHrqZMx1H0jLs59/FC1WibWZyEstgc7+N/1bRkC7tIicYSr0U4QjFfXFV CF/x8efgx9UPPQSJnM+WakwXapvWFFybFmL5XUrlJk1gAN0NMaJDLaFus1wnZao1Y2 UBRPbVF+Ejnl2CQusdrvY84v2+S+jX4Iso2sVyziNM9pOY7NXIJfLT1d1PS0AoLjXM h6haaafswXNwSADUYq3Ezy5Arf9rVtHE+zebxi6PIi6MgE818FYnDTvCBPWDZG7GXB JzUdItZrQEGxw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 2991CCE1408; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 09/12] rcutorture: Add reader_flavor parameter for SRCU readers Date: Wed, 9 Oct 2024 11:07:16 -0700 Message-Id: <20241009180719.778285-9-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit adds an rcutorture.reader_flavor parameter whose bits correspond to reader flavors. For example, SRCU's readers are 0x1 for normal and 0x2 for NMI-safe. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- .../admin-guide/kernel-parameters.txt | 8 +++++ kernel/rcu/rcutorture.c | 30 ++++++++++++++----- 2 files changed, 30 insertions(+), 8 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7edc5a5ba9c98..2d5a09ff6449b 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5421,6 +5421,14 @@ The delay, in seconds, between successive read-then-exit testing episodes. + rcutorture.reader_flavor= [KNL] + A bit mask indicating which readers to use. + If there is more than one bit set, the readers + are entered from low-order bit up, and are + exited in the opposite order. For SRCU, the + 0x1 bit is normal readers and the 0x2 bit is + for NMI-safe readers. + rcutorture.shuffle_interval= [KNL] Set task-shuffle interval (s). Shuffling tasks allows some CPUs to go into dyntick-idle mode diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index ea71a23b45d8b..daf60c988299d 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -111,6 +111,7 @@ torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disab torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)"); torture_param(int, read_exit_delay, 13, "Delay between read-then-exit episodes (s)"); torture_param(int, read_exit_burst, 16, "# of read-then-exit bursts per episode, zero to disable"); +torture_param(int, reader_flavor, 0x1, "Reader flavors to use, one per bit."); torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles"); torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable."); torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable."); @@ -646,10 +647,20 @@ static void srcu_get_gp_data(int *flags, unsigned long *gp_seq) static int srcu_torture_read_lock(void) { - if (cur_ops == &srcud_ops) - return srcu_read_lock_nmisafe(srcu_ctlp); - else - return srcu_read_lock(srcu_ctlp); + int idx; + int ret = 0; + + if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) { + idx = srcu_read_lock(srcu_ctlp); + WARN_ON_ONCE(idx & ~0x1); + ret += idx; + } + if (reader_flavor & 0x2) { + idx = srcu_read_lock_nmisafe(srcu_ctlp); + WARN_ON_ONCE(idx & ~0x1); + ret += idx << 1; + } + return ret; } static void @@ -673,10 +684,11 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) static void srcu_torture_read_unlock(int idx) { - if (cur_ops == &srcud_ops) - srcu_read_unlock_nmisafe(srcu_ctlp, idx); - else - srcu_read_unlock(srcu_ctlp, idx); + WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1))); + if (reader_flavor & 0x2) + srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1); + if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) + srcu_read_unlock(srcu_ctlp, idx & 0x1); } static int torture_srcu_read_lock_held(void) @@ -2404,6 +2416,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag) "n_barrier_cbs=%d " "onoff_interval=%d onoff_holdoff=%d " "read_exit_delay=%d read_exit_burst=%d " + "reader_flavor=%x " "nocbs_nthreads=%d nocbs_toggle=%d " "test_nmis=%d\n", torture_type, tag, nrealreaders, nfakewriters, @@ -2416,6 +2429,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag) n_barrier_cbs, onoff_interval, onoff_holdoff, read_exit_delay, read_exit_burst, + reader_flavor, nocbs_nthreads, nocbs_toggle, test_nmis); } From patchwork Wed Oct 9 18:07:17 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829006 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0EF91E1A34; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=FDVlhdNs53rflxJgYJxT8BMYzbeNUH2FTa6KdeJc6or+2Ys2Xv910MQDaIIZPgXn4bFib8xvhwb4A03uWJGEDvW20WfKIUkchIS+WJcOu1M7mpB4bcvUqPkljWsbMoe1tXBqTBaooYCZubtqt9Uoed7DBCcbuLphOU7IXSsnK68= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=QWCIBNJNmX4+TG7swbkj7aZiNkC9qbNnmlcDDakdbbQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=mMzjkNCiINupEIwMFC56Yl9H33qhtuDFqTJmsI0F+ctcTk4PGBLS7NLji1RBahnhvlMK/5bucmM+DrZa3o++0r0W3Me9Jc9Oz6xnkLhwyY6ds7Llyp1WXQ/DvvH88AOdbBlwL8MHGfJeGROq9D3GxrIxfGhfMgfMfz7GDn9wn54= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hA6hLzEp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hA6hLzEp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4443C4CEE0; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=QWCIBNJNmX4+TG7swbkj7aZiNkC9qbNnmlcDDakdbbQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hA6hLzEpFWyGDXIAMJn3qPtajMjZ0ydsTDW+K/ujmWL4Buwjrm8R+ZyS7U6fkhTkG QZrgPMneOetW0mb5wLhsmUvkZpuBgYK30KrYbUym3p8p9nYCWcntd+WJodPthm/4OB G8ZQZDL0lsDXdDXWb/p+FWJTa8hQCKlaGzbuX4f4cWC++aOYESOIjwPKVY97sRAPWV 6VTBy0JWHrvtZNmYsuPpwaYMdX7GIy7ACHTULxkL/EruzFZvMzWzrrgp/rWe/9WVvw 4cC4vvlFW/j14FkgJbGI/xq9W1X6F+CTnWHehoxGSybPbhjBUXmRh76+lqKYzKYV5s QrYKe8Piy2WIA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 2CD1FCE158E; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 10/12] rcutorture: Add srcu_read_lock_lite() support to rcutorture.reader_flavor Date: Wed, 9 Oct 2024 11:07:17 -0700 Message-Id: <20241009180719.778285-10-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit causes bit 0x4 of rcutorture.reader_flavor to select the new srcu_read_lock_lite() and srcu_read_unlock_lite() functions. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- Documentation/admin-guide/kernel-parameters.txt | 4 ++-- kernel/rcu/rcutorture.c | 7 +++++++ 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2d5a09ff6449b..686ea876a89c7 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5426,8 +5426,8 @@ If there is more than one bit set, the readers are entered from low-order bit up, and are exited in the opposite order. For SRCU, the - 0x1 bit is normal readers and the 0x2 bit is - for NMI-safe readers. + 0x1 bit is normal readers, 0x2 NMI-safe readers, + and 0x4 light-weight readers. rcutorture.shuffle_interval= [KNL] Set task-shuffle interval (s). Shuffling tasks diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index daf60c988299d..2ae8a5e5e99aa 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -660,6 +660,11 @@ static int srcu_torture_read_lock(void) WARN_ON_ONCE(idx & ~0x1); ret += idx << 1; } + if (reader_flavor & 0x4) { + idx = srcu_read_lock_lite(srcu_ctlp); + WARN_ON_ONCE(idx & ~0x1); + ret += idx << 2; + } return ret; } @@ -685,6 +690,8 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) static void srcu_torture_read_unlock(int idx) { WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1))); + if (reader_flavor & 0x4) + srcu_read_unlock_lite(srcu_ctlp, (idx & 0x4) >> 2); if (reader_flavor & 0x2) srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1); if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) From patchwork Wed Oct 9 18:07:18 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829011 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2AC541E1C25; Wed, 9 Oct 2024 18:07:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=klRIVeZrD8CNrZsYYUIlV7ZBsyzQN2tQ6D+sTtx21eyc9FpjOLoRNwJtGWRzrCBzVfy8pUCq8jjYkuoM8lfsgyO0i1DmnBhSXsAsOeESfzQ/EFlE4IpuUxvcyMm/o2i8ULc/HTerrM+1GguKYT+s6pRfdqbnWlU6JTUZFnpF+ok= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=aRxkj03S73hF0jV8gryZajtKN0A7DA6aTKR8Jq/1sgk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=LplFtQvntknIeQpkQqJUzzTwhPZl24mkh3xaQiu0YElucGOf0ZUc7Nb0HHmuywboOCFZ9o8uaCQEniUtAxotwXHQVKKVzrH8jkXAiSuDrDcbLYVjswF7i1cozWDVia5RByEJFq958/94IVs8VEmBVsXr4rN2buWLDj3P1mC1CF4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=M56uivsl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="M56uivsl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1A6DC4CEE3; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=aRxkj03S73hF0jV8gryZajtKN0A7DA6aTKR8Jq/1sgk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=M56uivslS80U3bDHqzXOPKBY9t3uuKNID6MTG9/Dz2WWpuCsFb19bJ/1JtfXvGqYt o8CIpd16zK/IBUY79iT4ErhQQR28b5Dz8ytETi0bAcMqVYHnxvbegLQ+v4Hofwvf4g YEj9QC2kp9gEM4a7UWu/sODFLyvLq9MXbtTbJKky6X0iIOKerjStKBoEKm3mjUELnN te5/Q7j6E1TDEpx1vXo9lCZCSmPFHLFxFk0epGgXwVcWckBGE9s8EDUT/OaewxbDN5 SnjBy8H88Q7zRLx/nCuC++T+p9wm3Zvn4F4IkaRboYByKb4A6/W2p/TlbwNFJXfuTo +rFP9GgJDntJg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 3068CCE1C55; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 11/12] rcutorture: Add light-weight SRCU scenario Date: Wed, 9 Oct 2024 11:07:18 -0700 Message-Id: <20241009180719.778285-11-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit adds an rcutorture scenario that tests light-weight SRCU readers. While in the area, it adjusts the size of the TREE10 scenario. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- tools/testing/selftests/rcutorture/configs/rcu/CFLIST | 1 + tools/testing/selftests/rcutorture/configs/rcu/SRCU-L | 10 ++++++++++ .../selftests/rcutorture/configs/rcu/SRCU-L.boot | 3 +++ .../selftests/rcutorture/configs/rcu/SRCU-N.boot | 1 + tools/testing/selftests/rcutorture/configs/rcu/TREE10 | 2 +- 5 files changed, 16 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCU-L create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot diff --git a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST index 98b6175e5aa09..45f572570a8c3 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST +++ b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST @@ -5,6 +5,7 @@ TREE04 TREE05 TREE07 TREE09 +SRCU-L SRCU-N SRCU-P SRCU-T diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L new file mode 100644 index 0000000000000..3b4fa8dbef8a9 --- /dev/null +++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L @@ -0,0 +1,10 @@ +CONFIG_RCU_TRACE=n +CONFIG_SMP=y +CONFIG_NR_CPUS=6 +CONFIG_HOTPLUG_CPU=y +CONFIG_PREEMPT_NONE=y +CONFIG_PREEMPT_VOLUNTARY=n +CONFIG_PREEMPT=n +#CHECK#CONFIG_RCU_EXPERT=n +CONFIG_KPROBES=n +CONFIG_FTRACE=n diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot new file mode 100644 index 0000000000000..0207b3138c5be --- /dev/null +++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot @@ -0,0 +1,3 @@ +rcutorture.torture_type=srcu +rcutorture.reader_flavor=0x4 +rcutorture.fwd_progress=3 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot index ce0694fd9b929..b54cf87dc1103 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot @@ -1,2 +1,3 @@ rcutorture.torture_type=srcu +rcutorture.reader_flavor=0x2 rcutorture.fwd_progress=3 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE10 b/tools/testing/selftests/rcutorture/configs/rcu/TREE10 index a323d8948b7cf..759ee51d3ddc6 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE10 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE10 @@ -1,5 +1,5 @@ CONFIG_SMP=y -CONFIG_NR_CPUS=56 +CONFIG_NR_CPUS=74 CONFIG_PREEMPT_NONE=y CONFIG_PREEMPT_VOLUNTARY=n CONFIG_PREEMPT=n From patchwork Wed Oct 9 18:07:19 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13829012 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2ACE61E1C27; Wed, 9 Oct 2024 18:07:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; cv=none; b=ZU1tRaQNMz8w/Ovb545TLFgNF/Q0bSi5Kp3W3+FIC8r6NV6rszfkupDd+1BZjrk1DvTzMJeMXqwOWdU4pPBMP/L9IbyBkMZLhu6eYOpPiNOO2xQ7gMNoer7EE3Sf77OEi/GHkR3HaFEOGpVq67ndQ1IjCZdTzJQfsf+djLrkj68= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728497242; c=relaxed/simple; bh=Am8qbMwuc4d4Iuj/D9Siigqz78XzeMZGAjUM0tNr9Ok=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=JfuGCpZj/V0cje+Kwk6WG+5AuUwf8TO2T7yFmEx2rWI2EJ4BwNkckviC0w3glJmvzCd4pAGXI0E4QCyVqJ22pVDXXrgmB9xpTQrdHcWWN2ufOj+6oSQfgyYu/j6zPp09aysWXcpOPwbdXoraUpuTN2gECDPaxzAbHqRlZDFqMdI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qvpQuhSg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qvpQuhSg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D20A9C4CEE6; Wed, 9 Oct 2024 18:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728497241; bh=Am8qbMwuc4d4Iuj/D9Siigqz78XzeMZGAjUM0tNr9Ok=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qvpQuhSgcrnfmB1VxjAkD2SLSay9WhILI/5HriHPtNESgCazoSBxu75AssIeIG2wN SM6uTRFf1it7J3XG4Lli+CW5p2/HYlsoLQRoGRNDDxm+vSFs01M0Wd3lsQUgTWxG9H ljfGH6kKV8qIBzopt78bS1rk9FBrDNtwGyioUgcs1p2eZizMvJShs6b4jRN8cTGVmY L6/9BW7aOJAc1v+Muq2Fmjw9L2RChw0C1AOPolRiIZHcCheArodrX9/L8xUuMMlf7T 6vNu3MR0QKp9CfGaC2b0XIdh1TgV2tN6RnBDSAuZI9ntgJVR36CM0uPOwA7CPBN9Hb dWKxCMy2zzvZQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 33CF9CE2325; Wed, 9 Oct 2024 11:07:21 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH rcu 12/12] refscale: Add srcu_read_lock_lite() support using "srcu-lite" Date: Wed, 9 Oct 2024 11:07:19 -0700 Message-Id: <20241009180719.778285-12-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This commit creates a new srcu-lite option for the refscale.scale_type module parameter that selects srcu_read_lock_lite() and srcu_read_unlock_lite(). Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/refscale.c | 51 +++++++++++++++++++++++++++++++++---------- 1 file changed, 40 insertions(+), 11 deletions(-) diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index be66e5a67ee19..897d5b5494949 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -216,6 +216,36 @@ static const struct ref_scale_ops srcu_ops = { .name = "srcu" }; +static void srcu_lite_ref_scale_read_section(const int nloops) +{ + int i; + int idx; + + for (i = nloops; i >= 0; i--) { + idx = srcu_read_lock_lite(srcu_ctlp); + srcu_read_unlock_lite(srcu_ctlp, idx); + } +} + +static void srcu_lite_ref_scale_delay_section(const int nloops, const int udl, const int ndl) +{ + int i; + int idx; + + for (i = nloops; i >= 0; i--) { + idx = srcu_read_lock_lite(srcu_ctlp); + un_delay(udl, ndl); + srcu_read_unlock_lite(srcu_ctlp, idx); + } +} + +static const struct ref_scale_ops srcu_lite_ops = { + .init = rcu_sync_scale_init, + .readsection = srcu_lite_ref_scale_read_section, + .delaysection = srcu_lite_ref_scale_delay_section, + .name = "srcu-lite" +}; + #ifdef CONFIG_TASKS_RCU // Definitions for RCU Tasks ref scale testing: Empty read markers. @@ -1133,27 +1163,26 @@ ref_scale_init(void) long i; int firsterr = 0; static const struct ref_scale_ops *scale_ops[] = { - &rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops, - &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &sched_clock_ops, &clock_ops, - &jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops, + &rcu_ops, &srcu_ops, &srcu_lite_ops, RCU_TRACE_OPS RCU_TASKS_OPS + &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, + &sched_clock_ops, &clock_ops, &jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops, + &typesafe_seqlock_ops, }; if (!torture_init_begin(scale_type, verbose)) return -EBUSY; for (i = 0; i < ARRAY_SIZE(scale_ops); i++) { - cur_ops = scale_ops[i]; - if (strcmp(scale_type, cur_ops->name) == 0) + cur_ops = scale_ops[i]; if (strcmp(scale_type, + cur_ops->name) == 0) break; } if (i == ARRAY_SIZE(scale_ops)) { - pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type); - pr_alert("rcu-scale types:"); - for (i = 0; i < ARRAY_SIZE(scale_ops); i++) + pr_alert("rcu-scale: invalid scale type: \"%s\"\n", + scale_type); pr_alert("rcu-scale types:"); for (i = 0; + i < ARRAY_SIZE(scale_ops); i++) pr_cont(" %s", scale_ops[i]->name); - pr_cont("\n"); - firsterr = -EINVAL; - cur_ops = NULL; + pr_cont("\n"); firsterr = -EINVAL; cur_ops = NULL; goto unwind; } if (cur_ops->init)