• Tejun Heo's avatar
    Freezer: Fix a race during freezing of TASK_STOPPED tasks · 8cfe400c
    Tejun Heo authored
    After calling freeze_task(), try_to_freeze_tasks() see whether the
    task is stopped or traced and if so, considers it to be frozen;
    however, nothing guarantees that either the task being frozen sees
    TIF_FREEZE or the freezer sees TASK_STOPPED -> TASK_RUNNING
    transition.  The task being frozen may wake up and not see TIF_FREEZE
    while the freezer fails to notice the transition and believes the task
    is still stopped.
    This patch fixes the race by making freeze_task() always go through
    fake_signal_wake_up() for applicable tasks.  The function goes through
    the target task's scheduler lock and thus guarantees that either the
    target sees TIF_FREEZE or try_to_freeze_task() sees TASK_RUNNING.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
freezer.c 4 KB