From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH] sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD
Date: Thu, 26 Aug 2021 19:04:08 +0200 [thread overview]
Message-ID: <20210826170408.vm7rlj7odslshwch@linutronix.de> (raw)
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
next reply other threads:[~2021-08-26 17:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-26 17:04 Sebastian Andrzej Siewior [this message]
2021-08-26 17:14 ` [PATCH] sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD Peter Zijlstra
2021-09-09 11:18 ` [tip: sched/core] " tip-bot2 for Sebastian Andrzej Siewior
2021-10-05 14:12 ` tip-bot2 for Sebastian Andrzej Siewior
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