From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72886C77B75 for ; Fri, 19 May 2023 17:21:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229912AbjESRVx (ORCPT ); Fri, 19 May 2023 13:21:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59318 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231779AbjESRV1 (ORCPT ); Fri, 19 May 2023 13:21:27 -0400 Received: from mail-pf1-x431.google.com (mail-pf1-x431.google.com [IPv6:2607:f8b0:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92DC51721 for ; Fri, 19 May 2023 10:21:08 -0700 (PDT) Received: by mail-pf1-x431.google.com with SMTP id d2e1a72fcca58-64d2b42a8f9so1239066b3a.3 for ; Fri, 19 May 2023 10:21:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1684516868; x=1687108868; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Ie3WjW8dWxj5WOSXB5283RQPy/3pGkianoLx2tVNmSE=; b=YFzuFJ4eWMAMLZhwqw3DBL6QSzTZYYa5+5StBECaLdL4G4pigB8ofT1gcUdimpiEex TUDIfFVtwz5+KlRL7JQHT2da3WMxmdqENRL5ms2CGY+2q3hdCV2Nt79wd9AtATEzbUlN 2n+bREyXkWhUEo1Yo+8a9WsEEPMByfDapf0rA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684516868; x=1687108868; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Ie3WjW8dWxj5WOSXB5283RQPy/3pGkianoLx2tVNmSE=; b=l80nn14j6IAfGbibHxjcogvQfAGRkfqFqzaJELgo/4lyNQB03O7/M7od4qfiLZkxnv Jcv9S6hXne5rTmjtxqIPkmd9uK8Ob414dEHXUMHJZtwY8+cdIz27bh7jd1bsrTA0Quii uIgDK/M2JAsU1LXfYYvsShNCXKo3466pqcxLbZWdjCGVpN5ohxkVOqJaEL5LDkz43Jkd IJtYfX9cqFvZcag16MgeoqY32pL/oii8mcpqZTp+bbasJ//EtC04gHxeY7rGctDbOXzS M+gJOAoENjKC+1PnLleslp52k0EyvaGOggNbPuj66VmPGY27wLysaZzjAl2+M046XJjs B1Fw== X-Gm-Message-State: AC+VfDzGDtrdOTKbpg1h54emUnfI/fiKS4RS5h14itmlFO2YVpTbzyUj jNPE3nE+h9oqhWY8JuwWlUdrUQ== X-Google-Smtp-Source: ACHHUZ7ATOZ4rrYyAkhTlLlxcJ+5wIJmhvaJz9egSunvv+DUCDA9ft5dxcoQbbZfEUNE16sB4U4I0A== X-Received: by 2002:a17:903:2343:b0:1ae:bf5:7a7 with SMTP id c3-20020a170903234300b001ae0bf507a7mr3990597plh.35.1684516867869; Fri, 19 May 2023 10:21:07 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:9b89:2dd0:d160:429d]) by smtp.gmail.com with ESMTPSA id gj19-20020a17090b109300b0024e4f169931sm1763835pjb.2.2023.05.19.10.21.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 May 2023 10:21:07 -0700 (PDT) From: Douglas Anderson To: Petr Mladek , Andrew Morton Cc: Matthias Kaehlcke , kgdb-bugreport@lists.sourceforge.net, Stephane Eranian , mpe@ellerman.id.au, Tzung-Bi Shih , Daniel Thompson , Mark Rutland , linuxppc-dev@lists.ozlabs.org, Sumit Garg , npiggin@gmail.com, davem@davemloft.net, Marc Zyngier , Stephen Boyd , sparclinux@vger.kernel.org, christophe.leroy@csgroup.eu, Catalin Marinas , ravi.v.shankar@intel.com, Randy Dunlap , Pingfan Liu , Guenter Roeck , Lecopzer Chen , Ian Rogers , ito-yuichi@fujitsu.com, ricardo.neri@intel.com, linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, Will Deacon , Chen-Yu Tsai , linux-kernel@vger.kernel.org, Masayoshi Mizuma , Andi Kleen , Douglas Anderson Subject: [PATCH v5 10/18] watchdog/hardlockup: Add a "cpu" param to watchdog_hardlockup_check() Date: Fri, 19 May 2023 10:18:34 -0700 Message-ID: <20230519101840.v5.10.I3a7d4dd8c23ac30ee0b607d77feb6646b64825c0@changeid> X-Mailer: git-send-email 2.40.1.698.g37aff9b760-goog In-Reply-To: <20230519101840.v5.18.Ia44852044cdcb074f387e80df6b45e892965d4a1@changeid> References: <20230519101840.v5.18.Ia44852044cdcb074f387e80df6b45e892965d4a1@changeid> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In preparation for the buddy hardlockup detector where the CPU checking for lockup might not be the currently running CPU, add a "cpu" parameter to watchdog_hardlockup_check(). As part of this change, make hrtimer_interrupts an atomic_t since now the CPU incrementing the value and the CPU reading the value might be different. Technially this could also be done with just READ_ONCE and WRITE_ONCE, but atomic_t feels a little cleaner in this case. While hrtimer_interrupts is made atomic_t, we change hrtimer_interrupts_saved from "unsigned long" to "int". The "int" is needed to match the data type backing atomic_t for hrtimer_interrupts. Even if this changes us from 64-bits to 32-bits (which I don't think is true for most compilers), it doesn't really matter. All we ever do is increment it every few seconds and compare it to an old value so 32-bits is fine (even 16-bits would be). The "signed" vs "unsigned" also doesn't matter for simple equality comparisons. hrtimer_interrupts_saved is _not_ switched to atomic_t nor even accessed with READ_ONCE / WRITE_ONCE. The hrtimer_interrupts_saved is always consistently accessed with the same CPU. NOTE: with the upcoming "buddy" detector there is one special case. When a CPU goes offline/online then we can change which CPU is the one to consistently access a given instance of hrtimer_interrupts_saved. We still can't end up with a partially updated hrtimer_interrupts_saved, however, because we end up petting all affected CPUs to make sure the new and old CPU can't end up somehow read/write hrtimer_interrupts_saved at the same time. Signed-off-by: Douglas Anderson --- Changes in v5: - Don't dump stack on the buddy CPU if we fail to backtrace the hung CPU. - Use atomic_t for hrtimer_interrupts. Changes in v4: - ("Add a "cpu" param to watchdog_hardlockup_check()") new for v4. include/linux/nmi.h | 2 +- kernel/watchdog.c | 52 ++++++++++++++++++++++++++---------------- kernel/watchdog_perf.c | 2 +- 3 files changed, 34 insertions(+), 22 deletions(-) diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 0c62c1bf0a71..92aa568c0c42 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -88,7 +88,7 @@ static inline void hardlockup_detector_disable(void) {} #endif #if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF) -void watchdog_hardlockup_check(struct pt_regs *regs); +void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs); #endif #if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 169e5dffbc00..2552e224f76a 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -87,29 +87,34 @@ __setup("nmi_watchdog=", hardlockup_panic_setup); #if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF) -static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); -static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); +static DEFINE_PER_CPU(atomic_t, hrtimer_interrupts); +static DEFINE_PER_CPU(int, hrtimer_interrupts_saved); static DEFINE_PER_CPU(bool, watchdog_hardlockup_warned); static unsigned long watchdog_hardlockup_all_cpu_dumped; -static bool is_hardlockup(void) +static bool is_hardlockup(unsigned int cpu) { - unsigned long hrint = __this_cpu_read(hrtimer_interrupts); + int hrint = atomic_read(&per_cpu(hrtimer_interrupts, cpu)); - if (__this_cpu_read(hrtimer_interrupts_saved) == hrint) + if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint) return true; - __this_cpu_write(hrtimer_interrupts_saved, hrint); + /* + * NOTE: we don't need any fancy atomic_t or READ_ONCE/WRITE_ONCE + * for hrtimer_interrupts_saved. hrtimer_interrupts_saved is + * written/read by a single CPU. + */ + per_cpu(hrtimer_interrupts_saved, cpu) = hrint; return false; } static void watchdog_hardlockup_kick(void) { - __this_cpu_inc(hrtimer_interrupts); + atomic_inc(raw_cpu_ptr(&hrtimer_interrupts)); } -void watchdog_hardlockup_check(struct pt_regs *regs) +void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs) { /* * Check for a hardlockup by making sure the CPU's timer @@ -117,35 +122,42 @@ void watchdog_hardlockup_check(struct pt_regs *regs) * fired multiple times before we overflow'd. If it hasn't * then this is a good indication the cpu is stuck */ - if (is_hardlockup()) { + if (is_hardlockup(cpu)) { unsigned int this_cpu = smp_processor_id(); + struct cpumask backtrace_mask = *cpu_online_mask; /* Only print hardlockups once. */ - if (__this_cpu_read(watchdog_hardlockup_warned)) + if (per_cpu(watchdog_hardlockup_warned, cpu)) return; - pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", this_cpu); + pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", cpu); print_modules(); print_irqtrace_events(current); - if (regs) - show_regs(regs); - else - dump_stack(); + if (cpu == this_cpu) { + if (regs) + show_regs(regs); + else + dump_stack(); + cpumask_clear_cpu(cpu, &backtrace_mask); + } else { + if (trigger_single_cpu_backtrace(cpu)) + cpumask_clear_cpu(cpu, &backtrace_mask); + } /* - * Perform all-CPU dump only once to avoid multiple hardlockups - * generating interleaving traces + * Perform multi-CPU dump only once to avoid multiple + * hardlockups generating interleaving traces */ if (sysctl_hardlockup_all_cpu_backtrace && !test_and_set_bit(0, &watchdog_hardlockup_all_cpu_dumped)) - trigger_allbutself_cpu_backtrace(); + trigger_cpumask_backtrace(&backtrace_mask); if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP"); - __this_cpu_write(watchdog_hardlockup_warned, true); + per_cpu(watchdog_hardlockup_warned, cpu) = true; } else { - __this_cpu_write(watchdog_hardlockup_warned, false); + per_cpu(watchdog_hardlockup_warned, cpu) = false; } } diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c index 04415812d079..4e60e8023515 100644 --- a/kernel/watchdog_perf.c +++ b/kernel/watchdog_perf.c @@ -120,7 +120,7 @@ static void watchdog_overflow_callback(struct perf_event *event, return; } - watchdog_hardlockup_check(regs); + watchdog_hardlockup_check(smp_processor_id(), regs); } static int hardlockup_detector_event_create(void) -- 2.40.1.698.g37aff9b760-goog