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watchdog/hardlockup: simplify perf event probe and remove per-cpu dependency 

Simplify the hardlockup detector's probe path and remove its implicit
dependency on pinned per-cpu execution.

Refactor hardlockup_detector_event_create() to be stateless.  Return the
created perf_event pointer to the caller instead of directly modifying the
per-cpu 'watchdog_ev' variable.  This allows the probe path to safely
manage a temporary event without the risk of leaving stale pointers should
task migration occur.

Link: https://lkml.kernel.org/r/20260129022629.2201331-1-realwujing@gmail.com
Signed-off-by: Shouxin Sun <sunshx@chinatelecom.cn>
Signed-off-by: Junnan Zhang <zhangjn11@chinatelecom.cn>
Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>
Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Jinchao Wang <wangjinchao600@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Huafei <lihuafei1@huawei.com>
Cc: Song Liu <song@kernel.org>
Cc: Thorsten Blum <thorsten.blum@linux.dev>
Cc: Wang Jinchao <wangjinchao600@gmail.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Qiliang Yuan 2026-01-28 21:26:14 -05:00 committed by Andrew Morton
parent 76149d5350
commit 0dddf20b4f
1 changed files with 28 additions and 22 deletions
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50
kernel/watchdog_perf.c
View File

@ -118,18 +118,11 @@ static void watchdog_overflow_callback(struct perf_event *event,
watchdog_hardlockup_check(smp_processor_id(), regs); watchdog_hardlockup_check(smp_processor_id(), regs);
} }
static int hardlockup_detector_event_create(void) static struct perf_event *hardlockup_detector_event_create(unsigned int cpu)
{ {
unsigned int cpu;
struct perf_event_attr *wd_attr; struct perf_event_attr *wd_attr;
struct perf_event *evt; struct perf_event *evt;
/*
* Preemption is not disabled because memory will be allocated.
* Ensure CPU-locality by calling this in per-CPU kthread.
*/
WARN_ON(!is_percpu_thread());
cpu = raw_smp_processor_id();
wd_attr = &wd_hw_attr; wd_attr = &wd_hw_attr;
wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
@ -143,14 +136,7 @@ static int hardlockup_detector_event_create(void)
watchdog_overflow_callback, NULL); watchdog_overflow_callback, NULL);
} }
if (IS_ERR(evt)) { return evt;
pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
PTR_ERR(evt));
return PTR_ERR(evt);
}
WARN_ONCE(this_cpu_read(watchdog_ev), "unexpected watchdog_ev leak");
this_cpu_write(watchdog_ev, evt);
return 0;
} }
/** /**
@ -159,17 +145,26 @@ static int hardlockup_detector_event_create(void)
*/ */
void watchdog_hardlockup_enable(unsigned int cpu) void watchdog_hardlockup_enable(unsigned int cpu)
{ {
struct perf_event *evt;
WARN_ON_ONCE(cpu != smp_processor_id()); WARN_ON_ONCE(cpu != smp_processor_id());
if (hardlockup_detector_event_create()) evt = hardlockup_detector_event_create(cpu);
if (IS_ERR(evt)) {
pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
PTR_ERR(evt));
return; return;
}
/* use original value for check */ /* use original value for check */
if (!atomic_fetch_inc(&watchdog_cpus)) if (!atomic_fetch_inc(&watchdog_cpus))
pr_info("Enabled. Permanently consumes one hw-PMU counter.\n"); pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
WARN_ONCE(this_cpu_read(watchdog_ev), "unexpected watchdog_ev leak");
this_cpu_write(watchdog_ev, evt);
watchdog_init_timestamp(); watchdog_init_timestamp();
perf_event_enable(this_cpu_read(watchdog_ev)); perf_event_enable(evt);
} }
/** /**
@ -263,19 +258,30 @@ bool __weak __init arch_perf_nmi_is_available(void)
*/ */
int __init watchdog_hardlockup_probe(void) int __init watchdog_hardlockup_probe(void)
{ {
struct perf_event *evt;
unsigned int cpu;
int ret; int ret;
if (!arch_perf_nmi_is_available()) if (!arch_perf_nmi_is_available())
return -ENODEV; return -ENODEV;
ret = hardlockup_detector_event_create(); if (!hw_nmi_get_sample_period(watchdog_thresh))
return -EINVAL;
if (ret) { /*
* Test hardware PMU availability by creating a temporary perf event.
* The event is released immediately.
*/
cpu = raw_smp_processor_id();
evt = hardlockup_detector_event_create(cpu);
if (IS_ERR(evt)) {
pr_info("Perf NMI watchdog permanently disabled\n"); pr_info("Perf NMI watchdog permanently disabled\n");
ret = PTR_ERR(evt);
} else { } else {
perf_event_release_kernel(this_cpu_read(watchdog_ev)); perf_event_release_kernel(evt);
this_cpu_write(watchdog_ev, NULL); ret = 0;
} }
return ret; return ret;
} }