From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Mike Galbraith <efault@gmx.de>
Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH RT 4/2] hrtimer: Don't lose state in cpu_chill()
Date: Tue, 26 Feb 2019 12:38:25 +0100 [thread overview]
Message-ID: <20190226113825.cusw372nwlbju4hh@linutronix.de> (raw)
In-Reply-To: <1551116436.5281.5.camel@gmx.de>
On 2019-02-25 18:40:36 [+0100], Mike Galbraith wrote:
> Ah. Yup, box says you're right.
Thank you. Added:
Subject: [PATCH] hrtimer: cpu_chill(): save task state in ->saved_state()
In the previous change I saved the current task state on stack. This was
bad because while the task is scheduled-out it might receive a wake-up.
The wake up changes the task state and we must not destroy it.
Save the task-state in ->saved_state under a PI-lock to unsure that
state changes during are not missed while the task temporary scheduled
out.
Reported-by: Mike Galbraith <efault@gmx.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/time/hrtimer.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 6f2736ec4b8ef..e1040b80362c9 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1900,20 +1900,28 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
*/
void cpu_chill(void)
{
- ktime_t chill_time;
unsigned int freeze_flag = current->flags & PF_NOFREEZE;
- long saved_state;
+ struct task_struct *self = current;
+ ktime_t chill_time;
- saved_state = current->state;
- chill_time = ktime_set(0, NSEC_PER_MSEC);
+ raw_spin_lock_irq(&self->pi_lock);
+ self->saved_state = self->state;
__set_current_state_no_track(TASK_UNINTERRUPTIBLE);
+ raw_spin_unlock_irq(&self->pi_lock);
+
+ chill_time = ktime_set(0, NSEC_PER_MSEC);
+
current->flags |= PF_NOFREEZE;
sleeping_lock_inc();
schedule_hrtimeout(&chill_time, HRTIMER_MODE_REL_HARD);
sleeping_lock_dec();
if (!freeze_flag)
current->flags &= ~PF_NOFREEZE;
- __set_current_state_no_track(saved_state);
+
+ raw_spin_lock_irq(&self->pi_lock);
+ __set_current_state_no_track(self->saved_state);
+ self->saved_state = TASK_RUNNING;
+ raw_spin_unlock_irq(&self->pi_lock);
}
EXPORT_SYMBOL(cpu_chill);
#endif
--
2.20.1
Sebastian
next prev parent reply other threads:[~2019-02-26 11:38 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-18 16:31 [PATCH RT 1/2] softirq: Avoid "local_softirq_pending" messages if ksoftirqd is blocked Sebastian Andrzej Siewior
2019-02-18 16:31 ` [PATCH RT 2/2] x86: lazy-preempt: properly check against preempt-mask Sebastian Andrzej Siewior
2019-02-19 16:07 ` [PATCH RT 3/2] softirq: Avoid "local_softirq_pending" messages if task is in cpu_chill() Sebastian Andrzej Siewior
2019-02-19 16:08 ` [PATCH RT 4/2] hrtimer: Don't lose state " Sebastian Andrzej Siewior
2019-02-25 14:43 ` Mike Galbraith
2019-02-25 16:34 ` Sebastian Andrzej Siewior
2019-02-25 17:40 ` Mike Galbraith
2019-02-26 11:38 ` Sebastian Andrzej Siewior [this message]
2019-02-19 14:58 ` [PATCH RT 1/2] softirq: Avoid "local_softirq_pending" messages if ksoftirqd is blocked Juri Lelli
2019-02-19 16:06 ` Sebastian Andrzej Siewior
2019-02-19 16:27 ` Juri Lelli
2019-02-19 16:28 ` Sebastian Andrzej Siewior
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