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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
	linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Carsten Emde <C.Emde@osadl.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	John Kacur <jkacur@redhat.com>, Daniel Wagner <wagi@monom.org>,
	Tom Zanussi <zanussi@kernel.org>,
	"Srivatsa S. Bhat" <srivatsa@csail.mit.edu>,
	stable-rt@vger.kernel.org
Subject: [PATCH RT 03/10] sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD
Date: Mon, 22 Nov 2021 15:38:50 -0500	[thread overview]
Message-ID: <20211122203903.858719209@goodmis.org> (raw)
In-Reply-To: <20211122203847.390551309@goodmis.org>

5.10.78-rt56-rc2 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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 an user
interface to abuse it and create a mass wake of several tasks at the
same time which would 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.

Cc: stable-rt@vger.kernel.org
Link: https://lkml.kernel.org/r/20210826170408.vm7rlj7odslshwch@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 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 f638d9420553..54fa3bb1b7c4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2734,7 +2734,7 @@ unsigned long wait_task_inactive(struct task_struct *p, long 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

  parent reply	other threads:[~2021-11-22 20:39 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-22 20:38 [PATCH RT 00/10] Linux 5.10.78-rt56-rc2 Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 01/10] mm, zsmalloc: Convert zsmalloc_handle.lock to spinlock_t Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 02/10] sched: Fix get_push_task() vs migrate_disable() Steven Rostedt
2021-11-22 20:38 ` Steven Rostedt [this message]
2021-11-22 20:38 ` [PATCH RT 04/10] preempt: Move preempt_enable_no_resched() to the RT block Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 05/10] mm: Disable NUMA_BALANCING_DEFAULT_ENABLED and TRANSPARENT_HUGEPAGE on PREEMPT_RT Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 06/10] fscache: Use only one fscache_object_cong_wait Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 07/10] fscache: Use only one fscache_object_cong_wait (2) Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 08/10] locking: Drop might_resched() from might_sleep_no_state_check() Steven Rostedt
2021-11-22 20:38 ` [PATCH RT 09/10] drm/i915/gt: Queue and wait for the irq_work item Steven Rostedt
2021-11-23  8:25   ` Sebastian Andrzej Siewior
2021-11-23 15:37     ` Steven Rostedt
2021-11-24 16:12       ` Sebastian Andrzej Siewior
2021-11-24 16:12         ` [PATCH RT 1/3] irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support Sebastian Andrzej Siewior
2021-11-24 16:12         ` [PATCH RT 2/3] irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RT Sebastian Andrzej Siewior
2021-11-24 16:12         ` [PATCH RT 3/3] irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ " Sebastian Andrzej Siewior
2021-11-22 20:38 ` [PATCH RT 10/10] Linux 5.10.78-rt56-rc2 Steven Rostedt

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