Messages in this thread Patch in this message | | | Date | Thu, 26 Aug 2021 19:04:08 +0200 | From | Sebastian Andrzej Siewior <> | Subject | [PATCH] sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD |
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With PREEMPT_RT enabled all hrtimers callbacks will be invoked in softirq mode unless they are explicitly marked as HRTIMER_MODE_HARD. During boot kthread_bind() is used for the creation of per-CPU threads and then hangs in wait_task_inactive() if the ksoftirqd is not yet up and running. The hang disappeared since commit 26c7295be0c5e ("kthread: Do not preempt current task if it is going to call schedule()")
but enabling function trace on boot reliably leads to the freeze on boot behaviour again. The timer in wait_task_inactive() can not be directly used by a user interface to abuse it and create a mass wake up of several tasks at the same time leading to long sections with disabled interrupts. Therefore it is safe to make the timer HRTIMER_MODE_REL_HARD.
Switch the timer to HRTIMER_MODE_REL_HARD.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 02718b6c7732d..3fbde6bc21bb2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3081,7 +3081,7 @@ unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state ktime_t to = NSEC_PER_SEC / HZ; set_current_state(TASK_UNINTERRUPTIBLE); - schedule_hrtimeout(&to, HRTIMER_MODE_REL); + schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); continue; } -- 2.33.0
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