• Tejun Heo's avatar
    freezer: make freezing indicate freeze condition in effect · 6907483b
    Tejun Heo authored
    Currently freezing (TIF_FREEZE) and frozen (PF_FROZEN) states are
    interlocked - freezing is set to request freeze and when the task
    actually freezes, it clears freezing and sets frozen.
    This interlocking makes things more complex than necessary - freezing
    doesn't mean there's freezing condition in effect and frozen doesn't
    match the task actually entering and leaving frozen state (it's
    cleared by the thawing task).
    This patch makes freezing indicate that freeze condition is in effect.
    A task enters and stays frozen if freezing.  This makes PF_FROZEN
    manipulation done only by the task itself and prevents wakeup from
    __thaw_task() leaking outside of refrigerator.
    The only place which needs to tell freezing && !frozen is
    try_to_freeze_task() to whine about tasks which don't enter frozen.
    It's updated to test the condition explicitly.
    With the change, frozen() state my linger after __thaw_task() until
    the task wakes up and exits fridge.  This can trigger BUG_ON() in
    update_if_frozen().  Work it around by testing freezing() && frozen()
    instead of frozen().
    -v2: Oleg pointed out missing re-check of freezing() when trying to
         clear FROZEN and possible spurious BUG_ON() trigger in
         update_if_frozen().  Both fixed.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Paul Menage <paul@paulmenage.org>
freezer.c 4.22 KB