From patchwork Wed Feb 28 07:22:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Bitao Hu X-Patchwork-Id: 13574935 Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) (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 CABD225108; Wed, 28 Feb 2024 07:22:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.100 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104957; cv=none; b=TWR8cH0KzcRk4MDyofduXQywmkK3nBFugNt4NEf2K+H4G6kS4k0ZuYI42IeL0G9jJ/ym/SU+90ApTXIhnNLx0F8N4CLVfX4yLeVSXRydEpxGpBAEC83piTejGFpvxXfAjNpGN3rAZG7p/yIHlm6nUqw7/xqPLESk1vC9+XTSM8I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104957; c=relaxed/simple; bh=YyGVL3DTq1NGBUlNTsaZWPygzXSkQqFhl2iQhk+tfEY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=td9WJ9IbEgBz8gKucbqwrbh4Jnmgu7SaEAkZITixQ3Wi2ak0VA/C7SoGZFtpg68I2rwimILOUdf9cQ93/MosQG8o3NgWVZ47UI5zFWle5L2tFCdSSYEB6Vdo2yVEHqYoHBrzQ+Nknt6D2LfEqvBepwP8Rd9S9gCyIJ7eyoThdA8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=E0v52FH2; arc=none smtp.client-ip=115.124.30.100 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="E0v52FH2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1709104947; h=From:To:Subject:Date:Message-Id:MIME-Version:Content-Type; bh=nB7HiCRDXz45RwbXKMqlhFZOk/rJjNAZ2WqhNw3OoCA=; b=E0v52FH26pRSogs/l5hN5vCxecONd6n2vqY+oWFE3KBA3G1SDa0e4UEKE70LXXdUwsE9IANXnuWthhctVT6OqbrSs/X+1r7iK3L/feUOTVybEQqqsLpml+DBajmA8rPoZ4zyGH/p7Gp1MuNf0mCr7lLucay0wvOj3uYxLgGYHXY= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=yaoma@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0W1P3Z2C_1709104943; Received: from localhost.localdomain(mailfrom:yaoma@linux.alibaba.com fp:SMTPD_---0W1P3Z2C_1709104943) by smtp.aliyun-inc.com; Wed, 28 Feb 2024 15:22:26 +0800 From: Bitao Hu To: dianders@chromium.org, tglx@linutronix.de, liusong@linux.alibaba.com, akpm@linux-foundation.org, pmladek@suse.com, kernelfans@gmail.com, deller@gmx.de, npiggin@gmail.com, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, jan.kiszka@siemens.com Cc: linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, yaoma@linux.alibaba.com Subject: [PATCHv11 1/4] watchdog/softlockup: low-overhead detection of interrupt storm Date: Wed, 28 Feb 2024 15:22:13 +0800 Message-Id: <20240228072216.95130-2-yaoma@linux.alibaba.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20240228072216.95130-1-yaoma@linux.alibaba.com> References: <20240228072216.95130-1-yaoma@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The following softlockup is caused by interrupt storm, but it cannot be identified from the call tree. Because the call tree is just a snapshot and doesn't fully capture the behavior of the CPU during the soft lockup. watchdog: BUG: soft lockup - CPU#28 stuck for 23s! [fio:83921] ... Call trace: __do_softirq+0xa0/0x37c __irq_exit_rcu+0x108/0x140 irq_exit+0x14/0x20 __handle_domain_irq+0x84/0xe0 gic_handle_irq+0x80/0x108 el0_irq_naked+0x50/0x58 Therefore，I think it is necessary to report CPU utilization during the softlockup_thresh period (report once every sample_period, for a total of 5 reportings), like this: watchdog: BUG: soft lockup - CPU#28 stuck for 23s! [fio:83921] CPU#28 Utilization every 4s during lockup: #1: 0% system, 0% softirq, 100% hardirq, 0% idle #2: 0% system, 0% softirq, 100% hardirq, 0% idle #3: 0% system, 0% softirq, 100% hardirq, 0% idle #4: 0% system, 0% softirq, 100% hardirq, 0% idle #5: 0% system, 0% softirq, 100% hardirq, 0% idle ... This would be helpful in determining whether an interrupt storm has occurred or in identifying the cause of the softlockup. The criteria for determination are as follows: a. If the hardirq utilization is high, then interrupt storm should be considered and the root cause cannot be determined from the call tree. b. If the softirq utilization is high, then we could analyze the call tree but it may cannot reflect the root cause. c. If the system utilization is high, then we could analyze the root cause from the call tree. The mechanism requires a considerable amount of global storage space when configured for the maximum number of CPUs. Therefore, adding a SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob that defaults to "yes" if the max number of CPUs is <= 128. Signed-off-by: Bitao Hu Reviewed-by: Douglas Anderson Reviewed-by: Liu Song --- kernel/watchdog.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++- lib/Kconfig.debug | 13 +++++++ 2 files changed, 110 insertions(+), 1 deletion(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 81a8862295d6..69e72d7e461d 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -16,6 +16,8 @@ #include #include #include +#include +#include #include #include #include @@ -35,6 +37,8 @@ static DEFINE_MUTEX(watchdog_mutex); # define WATCHDOG_HARDLOCKUP_DEFAULT 0 #endif +#define NUM_SAMPLE_PERIODS 5 + unsigned long __read_mostly watchdog_enabled; int __read_mostly watchdog_user_enabled = 1; static int __read_mostly watchdog_hardlockup_user_enabled = WATCHDOG_HARDLOCKUP_DEFAULT; @@ -333,6 +337,95 @@ __setup("watchdog_thresh=", watchdog_thresh_setup); static void __lockup_detector_cleanup(void); +#ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM +enum stats_per_group { + STATS_SYSTEM, + STATS_SOFTIRQ, + STATS_HARDIRQ, + STATS_IDLE, + NUM_STATS_PER_GROUP, +}; + +static const enum cpu_usage_stat tracked_stats[NUM_STATS_PER_GROUP] = { + CPUTIME_SYSTEM, + CPUTIME_SOFTIRQ, + CPUTIME_IRQ, + CPUTIME_IDLE, +}; + +static DEFINE_PER_CPU(u16, cpustat_old[NUM_STATS_PER_GROUP]); +static DEFINE_PER_CPU(u8, cpustat_util[NUM_SAMPLE_PERIODS][NUM_STATS_PER_GROUP]); +static DEFINE_PER_CPU(u8, cpustat_tail); + +/* + * We don't need nanosecond resolution. A granularity of 16ms is + * sufficient for our precision, allowing us to use u16 to store + * cpustats, which will roll over roughly every ~1000 seconds. + * 2^24 ~= 16 * 10^6 + */ +static u16 get_16bit_precision(u64 data_ns) +{ + return data_ns >> 24LL; /* 2^24ns ~= 16.8ms */ +} + +static void update_cpustat(void) +{ + int i; + u8 util; + u16 old_stat, new_stat; + struct kernel_cpustat kcpustat; + u64 *cpustat = kcpustat.cpustat; + u8 tail = __this_cpu_read(cpustat_tail); + u16 sample_period_16 = get_16bit_precision(sample_period); + + kcpustat_cpu_fetch(&kcpustat, smp_processor_id()); + + for (i = 0; i < NUM_STATS_PER_GROUP; i++) { + old_stat = __this_cpu_read(cpustat_old[i]); + new_stat = get_16bit_precision(cpustat[tracked_stats[i]]); + util = DIV_ROUND_UP(100 * (new_stat - old_stat), sample_period_16); + __this_cpu_write(cpustat_util[tail][i], util); + __this_cpu_write(cpustat_old[i], new_stat); + } + + __this_cpu_write(cpustat_tail, (tail + 1) % NUM_SAMPLE_PERIODS); +} + +static void print_cpustat(void) +{ + int i, group; + u8 tail = __this_cpu_read(cpustat_tail); + u64 sample_period_second = sample_period; + + do_div(sample_period_second, NSEC_PER_SEC); + + /* + * We do not want the "watchdog: " prefix on every line, + * hence we use "printk" instead of "pr_crit". + */ + printk(KERN_CRIT "CPU#%d Utilization every %llus during lockup:\n", + smp_processor_id(), sample_period_second); + + for (i = 0; i < NUM_SAMPLE_PERIODS; i++) { + group = (tail + i) % NUM_SAMPLE_PERIODS; + printk(KERN_CRIT "\t#%d: %3u%% system,\t%3u%% softirq,\t" + "%3u%% hardirq,\t%3u%% idle\n", i + 1, + __this_cpu_read(cpustat_util[group][STATS_SYSTEM]), + __this_cpu_read(cpustat_util[group][STATS_SOFTIRQ]), + __this_cpu_read(cpustat_util[group][STATS_HARDIRQ]), + __this_cpu_read(cpustat_util[group][STATS_IDLE])); + } +} + +static void report_cpu_status(void) +{ + print_cpustat(); +} +#else +static inline void update_cpustat(void) { } +static inline void report_cpu_status(void) { } +#endif + /* * Hard-lockup warnings should be triggered after just a few seconds. Soft- * lockups can have false positives under extreme conditions. So we generally @@ -364,7 +457,7 @@ static void set_sample_period(void) * and hard thresholds) to increment before the * hardlockup detector generates a warning */ - sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); + sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / NUM_SAMPLE_PERIODS); watchdog_update_hrtimer_threshold(sample_period); } @@ -504,6 +597,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) */ period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts)); + update_cpustat(); + /* Reset the interval when touched by known problematic code. */ if (period_ts == SOFTLOCKUP_DELAY_REPORT) { if (unlikely(__this_cpu_read(softlockup_touch_sync))) { @@ -539,6 +634,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); + report_cpu_status(); print_modules(); print_irqtrace_events(current); if (regs) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 975a07f9f1cc..49f652674bd8 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1029,6 +1029,19 @@ config SOFTLOCKUP_DETECTOR chance to run. The current stack trace is displayed upon detection and the system will stay locked up. +config SOFTLOCKUP_DETECTOR_INTR_STORM + bool "Detect Interrupt Storm in Soft Lockups" + depends on SOFTLOCKUP_DETECTOR && IRQ_TIME_ACCOUNTING + default y if NR_CPUS <= 128 + help + Say Y here to enable the kernel to detect interrupt storm + during "soft lockups". + + "soft lockups" can be caused by a variety of reasons. If one is + caused by an interrupt storm, then the storming interrupts will not + be on the callstack. To detect this case, it is necessary to report + the CPU stats and the interrupt counts during the "soft lockups". + config BOOTPARAM_SOFTLOCKUP_PANIC bool "Panic (Reboot) On Soft Lockups" depends on SOFTLOCKUP_DETECTOR From patchwork Wed Feb 28 07:22:14 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bitao Hu X-Patchwork-Id: 13574937 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) (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 D450B250FD; Wed, 28 Feb 2024 07:22:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.98 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104961; cv=none; b=hQG93AkerweFJII6dB+6H94J5d14+JTFGoBB1hyIJDz56W/1LRZ+2RBT2iPiMNpummrvMHXSz2/CPUcVODsOLDV+iEtlM5jJF/Po5r4qBK9ZJ2aHwjfG3F/ZL0391Vi5LOs0dYHrjZdp/Hc54NZfvqm/3bomRywuu4lo9zr02gQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104961; c=relaxed/simple; bh=kg6Y4XfjRDG7tDqX6V2YsxniF2NjgwXFAaN5jprutl0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=YfPm+dzLbzBGrDJF6pr6S9+QSVmPA3cVviogqe6c8ZFD4AZAvxd1B5iDinTmSvQfS0ELZhbNonS8VplOdPdpqD2r7Kc8DrHkAFAOZrrPkdCfpwUWcIYM/tN5QVaJmDG5pZqPBwuO0P+2qbMgzugpEvIt2PLWZpOEwb/EDradUJ0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=EKT0rKp3; arc=none smtp.client-ip=115.124.30.98 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="EKT0rKp3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1709104951; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=jOH2yaP9vEiLO4yFEkOCLZeIhxrZFKOR9l8gXL+XVoI=; b=EKT0rKp3mpuP6l+J0evyHtl71g5bMUcGAHkFm0QHDowVkLiujVJIk8rEPOEqE/CJhGbssFmvfaNGOOGMU5Y6hmChSIWdWH1UjoZJqA4KGWFVfng0APffAjz9VdA4m+gaYtT3yjaeByQrEezG/xPd1OY8xROItZyv+Lvu0ln8Qcw= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R371e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=yaoma@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0W1P3Z3p_1709104946; Received: from localhost.localdomain(mailfrom:yaoma@linux.alibaba.com fp:SMTPD_---0W1P3Z3p_1709104946) by smtp.aliyun-inc.com; Wed, 28 Feb 2024 15:22:29 +0800 From: Bitao Hu To: dianders@chromium.org, tglx@linutronix.de, liusong@linux.alibaba.com, akpm@linux-foundation.org, pmladek@suse.com, kernelfans@gmail.com, deller@gmx.de, npiggin@gmail.com, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, jan.kiszka@siemens.com Cc: linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, yaoma@linux.alibaba.com Subject: [PATCHv11 2/4] genirq: Provide a snapshot mechanism for interrupt statistics Date: Wed, 28 Feb 2024 15:22:14 +0800 Message-Id: <20240228072216.95130-3-yaoma@linux.alibaba.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20240228072216.95130-1-yaoma@linux.alibaba.com> References: <20240228072216.95130-1-yaoma@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The soft lockup detector lacks a mechanism to identify interrupt storms as root cause of a lockup. To enable this the detector needs a mechanism to snapshot the interrupt count statistics on a CPU when the detector observes a potential lockup scenario and compare that against the interrupt count when it warns about the lockup later on. The number of interrupts in that period give a hint whether the lockup might be caused by an interrupt storm. Instead of having extra storage in the lockup detector and accessing the internals of the interrupt descriptor directly, convert the per CPU irq_desc::kstat_irq member to a data structure which contains the counter plus a snapshot member and provide interfaces to take a snapshot of all interrupts on the current CPU and to retrieve the delta of a specific interrupt later on. Originally-by: Thomas Gleixner Signed-off-by: Bitao Hu Reviewed-by: Liu Song Reviewed-by: Douglas Anderson --- arch/mips/dec/setup.c | 2 +- arch/parisc/kernel/smp.c | 2 +- arch/powerpc/kvm/book3s_hv_rm_xics.c | 2 +- include/linux/irqdesc.h | 14 ++++++++++-- include/linux/kernel_stat.h | 3 +++ kernel/irq/internals.h | 2 +- kernel/irq/irqdesc.c | 34 ++++++++++++++++++++++------ kernel/irq/proc.c | 5 ++-- scripts/gdb/linux/interrupts.py | 6 ++--- 9 files changed, 51 insertions(+), 19 deletions(-) diff --git a/arch/mips/dec/setup.c b/arch/mips/dec/setup.c index 6c3704f51d0d..87f0a1436bf9 100644 --- a/arch/mips/dec/setup.c +++ b/arch/mips/dec/setup.c @@ -756,7 +756,7 @@ void __init arch_init_irq(void) NULL)) pr_err("Failed to register fpu interrupt\n"); desc_fpu = irq_to_desc(irq_fpu); - fpu_kstat_irq = this_cpu_ptr(desc_fpu->kstat_irqs); + fpu_kstat_irq = this_cpu_ptr(&desc_fpu->kstat_irqs->cnt); } if (dec_interrupt[DEC_IRQ_CASCADE] >= 0) { if (request_irq(dec_interrupt[DEC_IRQ_CASCADE], no_action, diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c index 444154271f23..800eb64e91ad 100644 --- a/arch/parisc/kernel/smp.c +++ b/arch/parisc/kernel/smp.c @@ -344,7 +344,7 @@ static int smp_boot_one_cpu(int cpuid, struct task_struct *idle) struct irq_desc *desc = irq_to_desc(i); if (desc && desc->kstat_irqs) - *per_cpu_ptr(desc->kstat_irqs, cpuid) = 0; + *per_cpu_ptr(desc->kstat_irqs, cpuid) = (struct irqstat) { }; } #endif diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c b/arch/powerpc/kvm/book3s_hv_rm_xics.c index e42984878503..f2636414d82a 100644 --- a/arch/powerpc/kvm/book3s_hv_rm_xics.c +++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c @@ -837,7 +837,7 @@ static inline void this_cpu_inc_rm(unsigned int __percpu *addr) */ static void kvmppc_rm_handle_irq_desc(struct irq_desc *desc) { - this_cpu_inc_rm(desc->kstat_irqs); + this_cpu_inc_rm(&desc->kstat_irqs->cnt); __this_cpu_inc(kstat.irqs_sum); } diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h index d9451d456a73..95d8def84471 100644 --- a/include/linux/irqdesc.h +++ b/include/linux/irqdesc.h @@ -17,6 +17,16 @@ struct irq_desc; struct irq_domain; struct pt_regs; +/** + * struct irqstat - interrupt statistics + * @cnt: real-time interrupt count + * @ref: snapshot of interrupt count + */ +struct irqstat { + unsigned int cnt; + unsigned int ref; +}; + /** * struct irq_desc - interrupt descriptor * @irq_common_data: per irq and chip data passed down to chip functions @@ -55,7 +65,7 @@ struct pt_regs; struct irq_desc { struct irq_common_data irq_common_data; struct irq_data irq_data; - unsigned int __percpu *kstat_irqs; + struct irqstat __percpu *kstat_irqs; irq_flow_handler_t handle_irq; struct irqaction *action; /* IRQ action list */ unsigned int status_use_accessors; @@ -119,7 +129,7 @@ extern struct irq_desc irq_desc[NR_IRQS]; static inline unsigned int irq_desc_kstat_cpu(struct irq_desc *desc, unsigned int cpu) { - return desc->kstat_irqs ? *per_cpu_ptr(desc->kstat_irqs, cpu) : 0; + return desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, cpu) : 0; } static inline struct irq_desc *irq_data_to_desc(struct irq_data *data) diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index 9935f7ecbfb9..98b3043ea5e6 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -79,6 +79,9 @@ static inline unsigned int kstat_cpu_softirqs_sum(int cpu) return sum; } +extern void kstat_snapshot_irqs(void); +extern unsigned int kstat_get_irq_since_snapshot(unsigned int irq); + /* * Number of interrupts per specific IRQ source, since bootup */ diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index bcc7f21db9ee..1d92532c2aae 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -258,7 +258,7 @@ static inline void irq_state_set_masked(struct irq_desc *desc) static inline void __kstat_incr_irqs_this_cpu(struct irq_desc *desc) { - __this_cpu_inc(*desc->kstat_irqs); + __this_cpu_inc(desc->kstat_irqs->cnt); __this_cpu_inc(kstat.irqs_sum); } diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 27ca1c866f29..9cd17080b2d8 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -122,7 +122,7 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node, desc->name = NULL; desc->owner = owner; for_each_possible_cpu(cpu) - *per_cpu_ptr(desc->kstat_irqs, cpu) = 0; + *per_cpu_ptr(desc->kstat_irqs, cpu) = (struct irqstat) { }; desc_smp_init(desc, node, affinity); } @@ -418,8 +418,8 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags, desc = kzalloc_node(sizeof(*desc), GFP_KERNEL, node); if (!desc) return NULL; - /* allocate based on nr_cpu_ids */ - desc->kstat_irqs = alloc_percpu(unsigned int); + + desc->kstat_irqs = alloc_percpu(struct irqstat); if (!desc->kstat_irqs) goto err_desc; @@ -593,7 +593,7 @@ int __init early_irq_init(void) count = ARRAY_SIZE(irq_desc); for (i = 0; i < count; i++) { - desc[i].kstat_irqs = alloc_percpu(unsigned int); + desc[i].kstat_irqs = alloc_percpu(struct irqstat); alloc_masks(&desc[i], node); raw_spin_lock_init(&desc[i].lock); lockdep_set_class(&desc[i].lock, &irq_desc_lock_class); @@ -952,8 +952,7 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu) { struct irq_desc *desc = irq_to_desc(irq); - return desc && desc->kstat_irqs ? - *per_cpu_ptr(desc->kstat_irqs, cpu) : 0; + return desc && desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, cpu) : 0; } static bool irq_is_nmi(struct irq_desc *desc) @@ -975,10 +974,31 @@ static unsigned int kstat_irqs(unsigned int irq) return data_race(desc->tot_count); for_each_possible_cpu(cpu) - sum += data_race(*per_cpu_ptr(desc->kstat_irqs, cpu)); + sum += data_race(per_cpu(desc->kstat_irqs->cnt, cpu)); return sum; } +void kstat_snapshot_irqs(void) +{ + struct irq_desc *desc; + unsigned int irq; + + for_each_irq_desc(irq, desc) { + if (!desc->kstat_irqs) + continue; + this_cpu_write(desc->kstat_irqs->ref, this_cpu_read(desc->kstat_irqs->cnt)); + } +} + +unsigned int kstat_get_irq_since_snapshot(unsigned int irq) +{ + struct irq_desc *desc = irq_to_desc(irq); + + if (!desc || !desc->kstat_irqs) + return 0; + return this_cpu_read(desc->kstat_irqs->cnt) - this_cpu_read(desc->kstat_irqs->ref); +} + /** * kstat_irqs_usr - Get the statistics for an interrupt from thread context * @irq: The interrupt number diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c index 623b8136e9af..6954e0a02047 100644 --- a/kernel/irq/proc.c +++ b/kernel/irq/proc.c @@ -490,7 +490,7 @@ int show_interrupts(struct seq_file *p, void *v) if (desc->kstat_irqs) { for_each_online_cpu(j) - any_count |= data_race(*per_cpu_ptr(desc->kstat_irqs, j)); + any_count |= data_race(per_cpu(desc->kstat_irqs->cnt, j)); } if ((!desc->action || irq_desc_is_chained(desc)) && !any_count) @@ -498,8 +498,7 @@ int show_interrupts(struct seq_file *p, void *v) seq_printf(p, "%*d: ", prec, i); for_each_online_cpu(j) - seq_printf(p, "%10u ", desc->kstat_irqs ? - *per_cpu_ptr(desc->kstat_irqs, j) : 0); + seq_printf(p, "%10u ", desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, j) : 0); raw_spin_lock_irqsave(&desc->lock, flags); if (desc->irq_data.chip) { diff --git a/scripts/gdb/linux/interrupts.py b/scripts/gdb/linux/interrupts.py index ef478e273791..7e50f3b9dfad 100644 --- a/scripts/gdb/linux/interrupts.py +++ b/scripts/gdb/linux/interrupts.py @@ -37,7 +37,7 @@ def show_irq_desc(prec, irq): any_count = 0 if desc['kstat_irqs']: for cpu in cpus.each_online_cpu(): - any_count += cpus.per_cpu(desc['kstat_irqs'], cpu) + any_count += cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt'] if (desc['action'] == 0 or irq_desc_is_chained(desc)) and any_count == 0: return text; @@ -45,7 +45,7 @@ def show_irq_desc(prec, irq): text += "%*d: " % (prec, irq) for cpu in cpus.each_online_cpu(): if desc['kstat_irqs']: - count = cpus.per_cpu(desc['kstat_irqs'], cpu) + count = cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt'] else: count = 0 text += "%10u" % (count) @@ -177,7 +177,7 @@ def arm_common_show_interrupts(prec): if desc == 0: continue for cpu in cpus.each_online_cpu(): - text += "%10u" % (cpus.per_cpu(desc['kstat_irqs'], cpu)) + text += "%10u" % (cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt']) text += " %s" % (ipi_types[ipi].string()) text += "\n" return text From patchwork Wed Feb 28 07:22:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bitao Hu X-Patchwork-Id: 13574936 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) (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 4365825114; Wed, 28 Feb 2024 07:22:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.99 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104960; cv=none; b=LbiyT1/65mik7D8Te9IdRwSoSMSl+AZzBbFOb4nZO0AYfs5H626Er3cY1tke+d2w7e1KOH4TqnHnAN8njqz16pmXJqeGMPLPaurxIwOkOKS+LgbCMgOm86ps2EGRuXST/duONLGmXVWM40vaa91QUyq+g/tq2rTg02pgNb4oJp4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104960; c=relaxed/simple; bh=1GTW3FB5egIhp784d5vJ5e2sJZgX2EBVdgdf8uBhCbc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=DNe47nJvXHdbHxGnOKkvF2d0P5djT55ViXBLufXhuNxzU4PpxYJDuVwFwQMa5AvTF0woqBQ7NlEA1e/ChwDrASxnm3P5rAaAG7wLyw1fCFsBokYJ6k6p/vYMoRk8DmiOZEL9X7ndhG1bg/umv/mDOWGl4sAaC+m7WrZRHo/098s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=UHYmNUS/; arc=none smtp.client-ip=115.124.30.99 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="UHYmNUS/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1709104955; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=9Vrc4ZqyAkRdothl4QztDqs6565tXq6hqjh9jwKlxdo=; b=UHYmNUS/oueSipx0mgHMmMepjK0t3N2XEDrfldxH2l5lWDX49Q6q6TpAAmJrwU1qui/Lasq4SJHkXESU4PGz/ny6XgNtMs0W45NQ6prL9no+cvEXInq1nidwcrUjccgEsfGIMJ3vxFPzqtXyx/2KiVEO3yWL+s0kU7PzDWn4xR8= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R711e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=yaoma@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0W1P3Z5L_1709104949; Received: from localhost.localdomain(mailfrom:yaoma@linux.alibaba.com fp:SMTPD_---0W1P3Z5L_1709104949) by smtp.aliyun-inc.com; Wed, 28 Feb 2024 15:22:32 +0800 From: Bitao Hu To: dianders@chromium.org, tglx@linutronix.de, liusong@linux.alibaba.com, akpm@linux-foundation.org, pmladek@suse.com, kernelfans@gmail.com, deller@gmx.de, npiggin@gmail.com, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, jan.kiszka@siemens.com Cc: linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, yaoma@linux.alibaba.com Subject: [PATCHv11 3/4] genirq: Avoid summation loops for /proc/interrupts Date: Wed, 28 Feb 2024 15:22:15 +0800 Message-Id: <20240228072216.95130-4-yaoma@linux.alibaba.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20240228072216.95130-1-yaoma@linux.alibaba.com> References: <20240228072216.95130-1-yaoma@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 show_interrupts() unconditionally accumulates the per CPU interrupt statistics to determine whether an interrupt was ever raised. This can be avoided for all interrupts which are not strictly per CPU and not of type NMI because those interrupts provide already an accumulated counter. The required logic is already implemented in kstat_irqs(). Split the inner access logic out of kstat_irqs() and use it for kstat_irqs() and show_interrupts() to avoid the accumulation loop when possible. Originally-by: Thomas Gleixner Signed-off-by: Bitao Hu Reviewed-by: Liu Song Reviewed-by: Douglas Anderson --- kernel/irq/internals.h | 2 ++ kernel/irq/irqdesc.c | 16 +++++++++++----- kernel/irq/proc.c | 6 ++---- 3 files changed, 15 insertions(+), 9 deletions(-) diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index 1d92532c2aae..6c43ef3e7308 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -98,6 +98,8 @@ extern void mask_irq(struct irq_desc *desc); extern void unmask_irq(struct irq_desc *desc); extern void unmask_threaded_irq(struct irq_desc *desc); +extern unsigned int kstat_irqs_desc(struct irq_desc *desc, const struct cpumask *cpumask); + #ifdef CONFIG_SPARSE_IRQ static inline void irq_mark_irq(unsigned int irq) { } #else diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 9cd17080b2d8..65a7f2dcd17b 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -960,24 +960,30 @@ static bool irq_is_nmi(struct irq_desc *desc) return desc->istate & IRQS_NMI; } -static unsigned int kstat_irqs(unsigned int irq) +unsigned int kstat_irqs_desc(struct irq_desc *desc, const struct cpumask *cpumask) { - struct irq_desc *desc = irq_to_desc(irq); unsigned int sum = 0; int cpu; - if (!desc || !desc->kstat_irqs) - return 0; if (!irq_settings_is_per_cpu_devid(desc) && !irq_settings_is_per_cpu(desc) && !irq_is_nmi(desc)) return data_race(desc->tot_count); - for_each_possible_cpu(cpu) + for_each_cpu(cpu, cpumask) sum += data_race(per_cpu(desc->kstat_irqs->cnt, cpu)); return sum; } +static unsigned int kstat_irqs(unsigned int irq) +{ + struct irq_desc *desc = irq_to_desc(irq); + + if (!desc || !desc->kstat_irqs) + return 0; + return kstat_irqs_desc(desc, cpu_possible_mask); +} + void kstat_snapshot_irqs(void) { struct irq_desc *desc; diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c index 6954e0a02047..5c320c3f10a7 100644 --- a/kernel/irq/proc.c +++ b/kernel/irq/proc.c @@ -488,10 +488,8 @@ int show_interrupts(struct seq_file *p, void *v) if (!desc || irq_settings_is_hidden(desc)) goto outsparse; - if (desc->kstat_irqs) { - for_each_online_cpu(j) - any_count |= data_race(per_cpu(desc->kstat_irqs->cnt, j)); - } + if (desc->kstat_irqs) + any_count = kstat_irqs_desc(desc, cpu_online_mask); if ((!desc->action || irq_desc_is_chained(desc)) && !any_count) goto outsparse; From patchwork Wed Feb 28 07:22:16 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bitao Hu X-Patchwork-Id: 13574938 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (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 3B00C25567; Wed, 28 Feb 2024 07:22:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.97 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709104962; cv=none; b=TfZrxTvijw7uAXuULGXAwuKr8R8ey7vNdfNDXhn0rW0wFfUUgUsSS9SbzKa2glQ/NyByH6fJUF51ltHsaFCIohUEycnWSQhwQ0pkTDFlg4OsUqrWco7VHr22FlOzhbkU1W/XSQM8sflZ3NHLmmYqC6lBECzkRpl8j5nudZ53Zm0= ARC-Message-Signature: i=1; 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a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1709104957; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=ypkMeHj6K2OB7ZjAbcREaWVLcPs4ICT4fmLAXzD0HaM=; b=PyPZQGblyDRSYlbdpy5HmZGYn5noUTzb2oSm8YeOOBe+/ihXw3PFQ49PY87nqSDOlGbPnNO7B/n1CyrrlN8Of8edwYGlGCAHcdfY5xrm7DedfmxFcHMrg26rrt9ivZ9PfpX1rTJ8SXY0bnooBTD1FF9ex6iXwqQBYqMuNSvEXis= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R211e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=yaoma@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0W1P3Z6U_1709104952; Received: from localhost.localdomain(mailfrom:yaoma@linux.alibaba.com fp:SMTPD_---0W1P3Z6U_1709104952) by smtp.aliyun-inc.com; Wed, 28 Feb 2024 15:22:35 +0800 From: Bitao Hu To: dianders@chromium.org, tglx@linutronix.de, liusong@linux.alibaba.com, akpm@linux-foundation.org, pmladek@suse.com, kernelfans@gmail.com, deller@gmx.de, npiggin@gmail.com, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, jan.kiszka@siemens.com Cc: linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, yaoma@linux.alibaba.com Subject: [PATCHv11 4/4] watchdog/softlockup: report the most frequent interrupts Date: Wed, 28 Feb 2024 15:22:16 +0800 Message-Id: <20240228072216.95130-5-yaoma@linux.alibaba.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20240228072216.95130-1-yaoma@linux.alibaba.com> References: <20240228072216.95130-1-yaoma@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 When the watchdog determines that the current soft lockup is due to an interrupt storm based on CPU utilization, reporting the most frequent interrupts could be good enough for further troubleshooting. Below is an example of interrupt storm. The call tree does not provide useful information, but we can analyze which interrupt caused the soft lockup by comparing the counts of interrupts. [ 638.870231] watchdog: BUG: soft lockup - CPU#9 stuck for 26s! [swapper/9:0] [ 638.870825] CPU#9 Utilization every 4s during lockup: [ 638.871194] #1: 0% system, 0% softirq, 100% hardirq, 0% idle [ 638.871652] #2: 0% system, 0% softirq, 100% hardirq, 0% idle [ 638.872107] #3: 0% system, 0% softirq, 100% hardirq, 0% idle [ 638.872563] #4: 0% system, 0% softirq, 100% hardirq, 0% idle [ 638.873018] #5: 0% system, 0% softirq, 100% hardirq, 0% idle [ 638.873494] CPU#9 Detect HardIRQ Time exceeds 50%. Most frequent HardIRQs: [ 638.873994] #1: 330945 irq#7 [ 638.874236] #2: 31 irq#82 [ 638.874493] #3: 10 irq#10 [ 638.874744] #4: 2 irq#89 [ 638.874992] #5: 1 irq#102 ... [ 638.875313] Call trace: [ 638.875315] __do_softirq+0xa8/0x364 Signed-off-by: Bitao Hu Reviewed-by: Liu Song Reviewed-by: Douglas Anderson --- kernel/watchdog.c | 115 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 111 insertions(+), 4 deletions(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 69e72d7e461d..c9d49ae8d045 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -12,22 +12,25 @@ #define pr_fmt(fmt) "watchdog: " fmt -#include #include -#include #include +#include +#include #include +#include #include +#include #include +#include +#include #include #include + #include #include #include -#include #include -#include static DEFINE_MUTEX(watchdog_mutex); @@ -417,13 +420,104 @@ static void print_cpustat(void) } } +#define HARDIRQ_PERCENT_THRESH 50 +#define NUM_HARDIRQ_REPORT 5 +struct irq_counts { + int irq; + u32 counts; +}; + +static DEFINE_PER_CPU(bool, snapshot_taken); + +/* Tabulate the most frequent interrupts. */ +static void tabulate_irq_count(struct irq_counts *irq_counts, int irq, u32 counts, int rank) +{ + int i; + struct irq_counts new_count = {irq, counts}; + + for (i = 0; i < rank; i++) { + if (counts > irq_counts[i].counts) + swap(new_count, irq_counts[i]); + } +} + +/* + * If the hardirq time exceeds HARDIRQ_PERCENT_THRESH% of the sample_period, + * then the cause of softlockup might be interrupt storm. In this case, it + * would be useful to start interrupt counting. + */ +static bool need_counting_irqs(void) +{ + u8 util; + int tail = __this_cpu_read(cpustat_tail); + + tail = (tail + NUM_HARDIRQ_REPORT - 1) % NUM_HARDIRQ_REPORT; + util = __this_cpu_read(cpustat_util[tail][STATS_HARDIRQ]); + return util > HARDIRQ_PERCENT_THRESH; +} + +static void start_counting_irqs(void) +{ + if (!__this_cpu_read(snapshot_taken)) { + kstat_snapshot_irqs(); + __this_cpu_write(snapshot_taken, true); + } +} + +static void stop_counting_irqs(void) +{ + __this_cpu_write(snapshot_taken, false); +} + +static void print_irq_counts(void) +{ + unsigned int i, count; + struct irq_counts irq_counts_sorted[NUM_HARDIRQ_REPORT] = { + {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0} + }; + + if (__this_cpu_read(snapshot_taken)) { + for_each_active_irq(i) { + count = kstat_get_irq_since_snapshot(i); + tabulate_irq_count(irq_counts_sorted, i, count, NUM_HARDIRQ_REPORT); + } + + /* + * We do not want the "watchdog: " prefix on every line, + * hence we use "printk" instead of "pr_crit". + */ + printk(KERN_CRIT "CPU#%d Detect HardIRQ Time exceeds %d%%. Most frequent HardIRQs:\n", + smp_processor_id(), HARDIRQ_PERCENT_THRESH); + + for (i = 0; i < NUM_HARDIRQ_REPORT; i++) { + if (irq_counts_sorted[i].irq == -1) + break; + + printk(KERN_CRIT "\t#%u: %-10u\tirq#%d\n", + i + 1, irq_counts_sorted[i].counts, + irq_counts_sorted[i].irq); + } + + /* + * If the hardirq time is less than HARDIRQ_PERCENT_THRESH% in the last + * sample_period, then we suspect the interrupt storm might be subsiding. + */ + if (!need_counting_irqs()) + stop_counting_irqs(); + } +} + static void report_cpu_status(void) { print_cpustat(); + print_irq_counts(); } #else static inline void update_cpustat(void) { } static inline void report_cpu_status(void) { } +static inline bool need_counting_irqs(void) { return false; } +static inline void start_counting_irqs(void) { } +static inline void stop_counting_irqs(void) { } #endif /* @@ -527,6 +621,18 @@ static int is_softlockup(unsigned long touch_ts, unsigned long now) { if ((watchdog_enabled & WATCHDOG_SOFTOCKUP_ENABLED) && watchdog_thresh) { + /* + * If period_ts has not been updated during a sample_period, then + * in the subsequent few sample_periods, period_ts might also not + * be updated, which could indicate a potential softlockup. In + * this case, if we suspect the cause of the potential softlockup + * might be interrupt storm, then we need to count the interrupts + * to find which interrupt is storming. + */ + if (time_after_eq(now, period_ts + get_softlockup_thresh() / NUM_SAMPLE_PERIODS) && + need_counting_irqs()) + start_counting_irqs(); + /* Warn about unreasonable delays. */ if (time_after(now, period_ts + get_softlockup_thresh())) return now - touch_ts; @@ -549,6 +655,7 @@ static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work); static int softlockup_fn(void *data) { update_touch_ts(); + stop_counting_irqs(); complete(this_cpu_ptr(&softlockup_completion)); return 0;