Commit 0dddf20b authored by Qiliang Yuan's avatar Qiliang Yuan Committed by Andrew Morton
Browse files

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: default avatarShouxin Sun <sunshx@chinatelecom.cn>
Signed-off-by: default avatarJunnan Zhang <zhangjn11@chinatelecom.cn>
Signed-off-by: default avatarQiliang Yuan <yuanql9@chinatelecom.cn>
Signed-off-by: default avatarQiliang Yuan <realwujing@gmail.com>
Reviewed-by: default avatarDouglas 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 76149d53

kernel/watchdog_perf.c

+28 −22
Original line number Diff line number Diff line
@@ -118,18 +118,11 @@ static void watchdog_overflow_callback(struct perf_event *event, 
	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 *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->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
@@ -143,14 +136,7 @@ static int hardlockup_detector_event_create(void) 
						       watchdog_overflow_callback, NULL);

	}



	if (IS_ERR(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;

	return evt;

}



/**
@@ -159,17 +145,26 @@ static int hardlockup_detector_event_create(void) 
 */

void watchdog_hardlockup_enable(unsigned int cpu)

{

	struct perf_event *evt;



	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;

	}



	/* use original value for check */

	if (!atomic_fetch_inc(&watchdog_cpus))

		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();

	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)

{

	struct perf_event *evt;

	unsigned int cpu;

	int ret;



	if (!arch_perf_nmi_is_available())

		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");

		ret = PTR_ERR(evt);

	} else {

		perf_event_release_kernel(this_cpu_read(watchdog_ev));

		this_cpu_write(watchdog_ev, NULL);

		perf_event_release_kernel(evt);

		ret = 0;

	}



	return ret;

}