Messages in this thread Patch in this message | | | From | Pingfan Liu <> | Subject | [PATCHv2 2/4] kernel/watchdog_hld: clarify the condition in hardlockup_detector_event_create() | Date | Thu, 23 Sep 2021 22:09:49 +0800 |
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As for the context, there are two arguments to change debug_smp_processor_id() to is_percpu_thread().
-1. watchdog_ev is percpu, and migration will frustrate the attempt which try to bind a watchdog_ev to a cpu by protecting this func inside the pair of preempt_disable()/preempt_enable().
-2. hardlockup_detector_event_create() indirectly calls kmem_cache_alloc_node(), which is blockable.
So here, spelling out the really planned context "is_percpu_thread()".
Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Wang Qing <wangqing@vivo.com> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Santosh Sivaraj <santosh@fossix.org> Cc: linux-arm-kernel@lists.infradead.org To: linux-kernel@vger.kernel.org --- kernel/watchdog_hld.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c index 247bf0b1582c..df010df76576 100644 --- a/kernel/watchdog_hld.c +++ b/kernel/watchdog_hld.c @@ -165,10 +165,13 @@ static void watchdog_overflow_callback(struct perf_event *event, static int hardlockup_detector_event_create(void) { - unsigned int cpu = smp_processor_id(); + unsigned int cpu; struct perf_event_attr *wd_attr; struct perf_event *evt; + /* This function plans to execute in cpu bound 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); -- 2.31.1
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