• Tejun Heo's avatar
    cgroup_freezer: prepare for removal of TIF_FREEZE · 22b4e111
    Tejun Heo authored
    TIF_FREEZE will be removed soon and freezing() will directly test
    whether any freezing condition is in effect.  Make the following
    changes in preparation.
    
    * Rename cgroup_freezing_or_frozen() to cgroup_freezing() and make it
      return bool.
    
    * Make cgroup_freezing() access task_freezer() under rcu read lock
      instead of task_lock().  This makes the state dereferencing racy
      against task moving to another cgroup; however, it was already racy
      without this change as ->state dereference wasn't synchronized.
      This will be later dealt with using attach hooks.
    
    * freezer->state is now set before trying to push tasks into the
      target state.
    
    -v2: Oleg pointed out that freeze_change_state() was setting
         freeze->state incorrectly to CGROUP_FROZEN instead of
         CGROUP_FREEZING.  Fixed.
    
    -v3: Matt pointed out that setting CGROUP_FROZEN used to always invoke
         try_to_freeze_cgroup() regardless of the current state.  Patch
         updated such that the actual freeze/thaw operations are always
         performed on invocation.  This shouldn't make any difference
         unless something is broken.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Acked-by: default avatarPaul Menage <paul@paulmenage.org>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    22b4e111
cgroup_freezer.c 9.03 KB