Re: [PATCH v2 2/3] mutex: add support for reservation style locks,v2

[Peter Zijlstra]

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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