freezer: use dedicated lock instead of task_lock() + memory barrier

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Freezer synchronization is needlessly complicated - it's by no means a
hot path and the priority is staying unintrusive and safe.  This patch
makes it simply use a dedicated lock instead of piggy-backing on
task_lock() and playing with memory barriers.

On the failure path of try_to_freeze_tasks(), locking is moved from it
to cancel_freezing().  This makes the frozen() test racy but the race
here is a non-issue as the warning is printed for tasks which failed
to enter frozen for 20 seconds and race on PF_FROZEN at the last
moment doesn't change anything.

This simplifies freezer implementation and eases further changes
including some race fixes.

Signed-off-by: Tejun Heo <tj@kernel.org>

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This commit is contained in:

Tejun Heo 2011-11-21 12:32:24 -08:00

parent 6cd8dedcdd

commit 0c9af09262

2 changed files with 37 additions and 49 deletions

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82

kernel/freezer.c

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2

kernel/power/process.c

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