From patchwork Fri Aug 16 04:39:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Neeraj Upadhyay X-Patchwork-Id: 13765436 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 CAD837D07E; Fri, 16 Aug 2024 04:40:03 +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=1723783203; cv=none; b=TkmHmUQC0ucdMhrvBh0oKRKZKER/Sl+ZUrHKoP3LxqIov27dSciz/d9DkpN3HUVBpSSgrPU/Tax9d84QRT43Inhx+kH2RLYj6zp0RooYL3fZrOcyyq4gJ65iwOXVyZZ+1mDEcrh9KNNvz+vEc3celcgE7uw+DiXmu4c8rCLlr9c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723783203; c=relaxed/simple; bh=J89s7BvJjaodUbVqWIXuLyWtkXirVXq4up0wxHeWgqw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=NSUTaLlImmNhwPfMCLLUuSsvmmZKQ463+xopUcz15iG3xy5OdLL56ufwL2+rFUiFvFV9sYG/McaINh6pkVyjVeGq2FJFQ/dZPnZoYAaTp9ZppmD7Z7G+mngXiNdKqlu+VDhAsGgVYOEGTe6NQJBe2SGaNaPxONyzNddXa0ib/lw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RkZ4HP88; 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="RkZ4HP88" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61278C4AF0E; Fri, 16 Aug 2024 04:39:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723783203; bh=J89s7BvJjaodUbVqWIXuLyWtkXirVXq4up0wxHeWgqw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RkZ4HP88N78dCZAVe35PCZTIyGNM95HZt0VsuJbh2C8s0mK3XxkNdiJcpBSCt22Or J3+w+iKZb7BluE5Cp09vdLhUnzlCN6wERR2ziEiuUX7NWFNY3FdGYO+9Z9/WWn+k98 B1kg6IZmQPVP2zB+QprbxcWB1mOBM32vGBlMd56I0Dj6ZW8v8vnZIGb3/YXGosG2mT WylPPpsJefVeXKH/84sLVSwcGCjLWIiR8qeZkrV4UDKNboXc+pC/vQiMMeF5sYyb+U 8Grzv4iKrVatpUUO8s+mrxROfjOqG2JKQnDlU9LDsdsAH9ZNWVmAXsmD5AI6MHhjbE Phg+33rqHZn+g== From: neeraj.upadhyay@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, paulmck@kernel.org, neeraj.upadhyay@kernel.org, neeraj.upadhyay@amd.com, boqun.feng@gmail.com, joel@joelfernandes.org, urezki@gmail.com, frederic@kernel.org, mingo@kernel.org, peterz@infradead.org, leobras@redhat.com, imran.f.khan@oracle.com, riel@surriel.com, tglx@linutronix.de Subject: [PATCH rcu 2/4] locking/csd_lock: Provide an indication of ongoing CSD-lock stall Date: Fri, 16 Aug 2024 10:09:15 +0530 Message-Id: <20240816043917.26537-2-neeraj.upadhyay@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240816043600.GA25206@neeraj.linux> References: <20240816043600.GA25206@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. [ neeraj.upadhyay: Apply Rik van Riel feedback. ] [ neeraj.upadhyay: Apply kernel test robot feedback. ] 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 ++++++++++++++++ lib/Kconfig.debug | 1 + 3 files changed, 23 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 e87953729230..202cda4d2a55 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -208,6 +208,19 @@ 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, @@ -229,6 +242,7 @@ 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; } @@ -252,6 +266,8 @@ 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_inc(&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 diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index a30c03a66172..4e5f61cba8e4 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1614,6 +1614,7 @@ config SCF_TORTURE_TEST config CSD_LOCK_WAIT_DEBUG bool "Debugging for csd_lock_wait(), called from smp_call_function*()" depends on DEBUG_KERNEL + depends on SMP depends on 64BIT default n help