From patchwork Sat Jul 13 16:58:45 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Neeraj Upadhyay X-Patchwork-Id: 13732455 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 114CB13B287; Sat, 13 Jul 2024 16:59:36 +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=1720889977; cv=none; b=R+zXDOlUNYjd3qddZYjGIIA0w+yCVvVTyqha7ZtgFkYrNLr7ad172Qsujuo8TUNPBBlRZF+lJe/wVApnY6kGsR7waGJ5P+NPQu45REclTbutbNA2vSVMrgATxrCIkOrWGzydzA6VJmwOut5745CpqPL6v12FLrjDuM6vvGbhQAQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720889977; c=relaxed/simple; bh=TcTKuYb/T3TiNi95YK/ATJr+aH6f3xo82T3OOyXeLDk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=iXFCf/4TiGT9zrEH4FG1QJyHpFOlMMez51q8VuM0/KYX3cKZtwzndo+nCv0UNbNCrQJ+ih6Ajk+A+LM4p2QJ0xfoEnCVOEHlK3OX4Tw3531SUJdwcch3rGuOiZhOklt5YpdKeZYOIeX/Sh9VTL4iigHCHmcOuIPRPHZttDScOvc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=K0fbpG8q; 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="K0fbpG8q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D130C32781; Sat, 13 Jul 2024 16:59:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720889976; bh=TcTKuYb/T3TiNi95YK/ATJr+aH6f3xo82T3OOyXeLDk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=K0fbpG8qQirQk8feTGjpFY02fyuc0mVKjAKBkKo/N+FJTtWMj0Ruvbsfagt9LH5RH XqEQzqx4NWcZ6ho0utqjKWCGG0YFJc498P5cEte+5x79z/gFdvM/lvkB1ghr0P0Y84 YDO0qF7EghCSEHxjDKcKEI71WSL/deSJRzYIsw6g+EuYHpkQL3AnipOGXdd65dSQYa LQHPG7bU1EE9uB6WYZLG0rdo7brKuk2LXGkQMqXoMS3BEWzEsqXIlIHce7UchkV8WP NdDweL6GtNxEWw2BawsIuTY5JhatYtg2lF4EXBva2pULVkOCLVcj+Emp4cx6IWpK9W BelPT7o+yuDRw== From: neeraj.upadhyay@kernel.org To: linux-kernel@vger.kernel.org Cc: rcu@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, mingo@kernel.org, peterz@infradead.org, paulmck@kernel.org, leobras@redhat.com, imran.f.khan@oracle.com, riel@surriel.com, neeraj.upadhyay@kernel.org Subject: [PATCH 2/3] locking/csd_lock: Provide an indication of ongoing CSD-lock stall Date: Sat, 13 Jul 2024 22:28:45 +0530 Message-Id: <20240713165846.216174-2-neeraj.upadhyay@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240713165642.GA215331@neeraj.linux> References: <20240713165642.GA215331@neeraj.linux> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Paul E. McKenney" If a CSD-lock stall goes on long enough, it will cause an RCU CPU stall warning. This additional warning provides much additional console-log traffic and little additional information. Therefore, provide a new csd_lock_is_stuck() function that returns true if there is an ongoing CSD-lock stall. This function will be used by the RCU CPU stall warnings to provide a one-line indication of the stall when this function returns true. Signed-off-by: Paul E. McKenney Cc: Imran Khan Cc: Ingo Molnar Cc: Leonardo Bras Cc: "Peter Zijlstra (Intel)" Cc: Rik van Riel Signed-off-by: Neeraj Upadhyay --- include/linux/smp.h | 6 ++++++ kernel/smp.c | 16 ++++++++++++++++ 2 files changed, 22 insertions(+) diff --git a/include/linux/smp.h b/include/linux/smp.h index fcd61dfe2af3..3871bd32018f 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -294,4 +294,10 @@ int smpcfd_prepare_cpu(unsigned int cpu); int smpcfd_dead_cpu(unsigned int cpu); int smpcfd_dying_cpu(unsigned int cpu); +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG +bool csd_lock_is_stuck(void); +#else +static inline bool csd_lock_is_stuck(void) { return false; } +#endif + #endif /* __LINUX_SMP_H */ diff --git a/kernel/smp.c b/kernel/smp.c index 81f7083a53e2..c3e8241e9cbb 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -207,6 +207,19 @@ static int csd_lock_wait_getcpu(call_single_data_t *csd) return -1; } +static atomic_t n_csd_lock_stuck; + +/** + * csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long? + * + * Returns @true if a CSD-lock acquisition is stuck and has been stuck + * long enough for a "non-responsive CSD lock" message to be printed. + */ +bool csd_lock_is_stuck(void) +{ + return !!atomic_read(&n_csd_lock_stuck); +} + /* * Complain if too much time spent waiting. Note that only * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, @@ -228,6 +241,7 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in cpu = csd_lock_wait_getcpu(csd); pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", *bug_id, raw_smp_processor_id(), cpu); + atomic_dec(&n_csd_lock_stuck); return true; } @@ -251,6 +265,8 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n", firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta, cpu, csd->func, csd->info); + if (firsttime) + atomic_dec(&n_csd_lock_stuck); /* * If the CSD lock is still stuck after 5 minutes, it is unlikely * to become unstuck. Use a signed comparison to avoid triggering