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@xxxxxx>
Tested-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
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
