From patchwork Sat Jul 13 16:58:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Neeraj Upadhyay X-Patchwork-Id: 13732456 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 863D213B287; Sat, 13 Jul 2024 16:59:41 +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=1720889981; cv=none; b=Hc6bjOcjuUUjrmYP4/qOgOLLdZ/AI0/tUk1ppIBhzGreeii+2hHrxoEqF893DjoaJEknmV71NMALSpDWhFLhDd77n/d7r0ft3csOGgfrYLKt7oHYwDVEoHTpUOonhN4i70HATIL9CZR5bUsz+gdlZmyQxz7c8v+UJSiLnMm0zng= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720889981; c=relaxed/simple; bh=GLt0F51yTmhEBaXCELRw+d8hd96JhxGIjc0n17/Yv3I=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=VU+KqG/sEdzEFSua/3zQUeyGauOqNboWr4+JHC+EsufQRh2arWNprgQsUWSsPUVm64YpVridbuGK64xj9Gur/cBDM5q+Ne9vq30y+rY90Kk3T2bZpiGLULTZNImYtb9jdIgzOd/cwylKrlzbq2NYrOZzF4RRkzdnel8X/8X57aM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V7MLAuAn; 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="V7MLAuAn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EFFC0C32786; Sat, 13 Jul 2024 16:59:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720889981; bh=GLt0F51yTmhEBaXCELRw+d8hd96JhxGIjc0n17/Yv3I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V7MLAuAnvCXX7QlIoZtI9Tpdpflj+8SslgEiDYbw1AIZ1Kwfhc5Z8ajOtwUQ0AkKR xgihewkRHSNVJazZLBsKGPgjev0BJV19it0IjWO4VdfItGIitVbTv4KtECdbIfktAN ZihTRB+jOJB4vF6mTVWBIufkR59BjxWuWFBlMtcaPcKs8iEdQTAXwrTBN6BuybKRnk BJ1FXnY/ifiiMv9Fi+6ATJ/x5KcXKADn3+mShFN65F/TvlTFPROVly//fwJz6tV5/3 dPSCLOu40dZC2pfMPAqcmSHQdKkqsVRfBS/J70lnR+bG5Z01yUBg87Nir8cW/CXA2x TI12pfDpvtUiA== 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 3/3] locking/csd-lock: Use backoff for repeated reports of same incident Date: Sat, 13 Jul 2024 22:28:46 +0530 Message-Id: <20240713165846.216174-3-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" Currently, the CSD-lock diagnostics in CONFIG_CSD_LOCK_WAIT_DEBUG=y kernels are emitted at five-second intervals. Although this has proven to be a good time interval for the first diagnostic, if the target CPU keeps interrupts disabled for way longer than five seconds, the ratio of useful new information to pointless repetition increases considerably. Therefore, back off the time period for repeated reports of the same incident, increasing linearly with the number of reports and logarithmicly with the number of online CPUs. [ paulmck: Apply Dan Carpenter 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 Reviewed-by: Rik van Riel --- kernel/smp.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index c3e8241e9cbb..80c1173ce369 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -225,7 +225,7 @@ bool csd_lock_is_stuck(void) * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, * so waiting on other types gets much less information. */ -static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id) +static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages) { int cpu = -1; int cpux; @@ -248,7 +248,9 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in ts2 = sched_clock(); /* How long since we last checked for a stuck CSD lock.*/ ts_delta = ts2 - *ts1; - if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0)) + if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) * + (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) || + csd_lock_timeout_ns == 0)) return false; firsttime = !*bug_id; @@ -265,6 +267,7 @@ 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); + (*nmessages)++; if (firsttime) atomic_dec(&n_csd_lock_stuck); /* @@ -305,12 +308,13 @@ static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, in */ static void __csd_lock_wait(call_single_data_t *csd) { + unsigned long nmessages = 0; int bug_id = 0; u64 ts0, ts1; ts1 = ts0 = sched_clock(); for (;;) { - if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id)) + if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages)) break; cpu_relax(); }