From: Sebastian Andrzej Siewior Date: Tue, 26 Feb 2019 12:31:10 +0100 Subject: [PATCH 184/351] hrtimer: cpu_chill(): save task state in ->saved_state() Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=781af25fa18a1586f4a6e1690b49521a79ebd7cf 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 Tested-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- 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 96e505abf939..aa8f3177580a 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1967,20 +1967,28 @@ 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