• Tejun Heo's avatar
    freezer: fix current->state restoration race in refrigerator() · 50fb4f7f
    Tejun Heo authored
    refrigerator() saves current->state before entering frozen state and
    restores it before returning using __set_current_state(); however,
    this is racy, for example, please consider the following sequence.
    	if (kthread_should_stop())
    If kthread_stop() races with ->state restoration, the restoration can
    restore ->state to TASK_INTERRUPTIBLE after kthread_stop() sets it to
    TASK_RUNNING but kthread_should_stop() may still see zero
    ->should_stop because there's no memory barrier between restoring
    TASK_INTERRUPTIBLE and kthread_should_stop() test.
    This isn't restricted to kthread_should_stop().  current->state is
    often used in memory barrier based synchronization and silently
    restoring it w/o mb breaks them.
    Use set_current_state() instead.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
freezer.c 4.2 KB