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freezer: test freezable conditions while holding freezer_lock

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try_to_freeze_tasks() and thaw_processes() use freezable() and
frozen() as preliminary tests before initiating operations on a task.
These are done without any synchronization and hinder with
synchronization cleanup without any real performance benefits.

In try_to_freeze_tasks(), open code self test and move PF_NOFREEZE and
frozen() tests inside freezer_lock in freeze_task().

thaw_processes() can simply drop freezable() test as frozen() test in
__thaw_task() is enough.

Note: This used to be a part of larger patch to fix set_freezable()
      race.  Separated out to satisfy ordering among dependent fixes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
This commit is contained in:
Tejun Heo 2011-11-21 12:32:24 -08:00
parent 6907483b4e
commit 85f1d47665
2 changed files with 3 additions and 16 deletions
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3
kernel/freezer.c
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@ -109,7 +109,8 @@ bool freeze_task(struct task_struct *p, bool sig_only)
spin_lock_irqsave(&freezer_lock, flags);
if (sig_only && !should_send_signal(p))
if ((p->flags & PF_NOFREEZE) ||
(sig_only && !should_send_signal(p)))
goto out_unlock;
if (frozen(p))