[PATCH v2 2/3] mutex: add support for reservation style locks, v2
Peter Zijlstra
peterz at infradead.org
Thu Apr 4 09:38:36 PDT 2013
On Thu, 2013-04-04 at 15:31 +0200, Daniel Vetter wrote:
> Hm, I guess your aim with the TASK_DEADLOCK wakeup is to bound the
> wait
> times of older task.
No, imagine the following:
struct ww_mutex A, B;
struct mutex C;
task-O task-Y task-X
A
B
C
C
B
At this point O finds that Y owns B and thus we want to make Y 'yield'
B to make allow B progress. Since Y is blocked, we'll send a wakeup.
However Y is blocked on a different locking primitive; one that doesn't
collaborate in the -EDEADLK scheme therefore we don't want the wakeup to
succeed.
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