Messages in this thread | | | Date | Mon, 23 May 2016 14:31:23 -0700 | From | Davidlohr Bueso <> | Subject | Re: [PATCH] locking/mutex: Set and clear owner using WRITE_ONCE() |
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On Mon, 23 May 2016, Jason Low wrote:
>On Fri, 2016-05-20 at 18:00 -0700, Davidlohr Bueso wrote: >> On Fri, 20 May 2016, Waiman Long wrote: >> >> >I think mutex-debug.h also needs similar changes for completeness. >> >> Maybe, but given that with debug the wait_lock is unavoidable, doesn't >> this send the wrong message? > >The mutex_set_owner() and mutex_clear_owner() can still get called in >the fastpath without the wait_lock for the debug case too correct?
The fastpath is a nop, see mutex-null:
#define __mutex_fastpath_lock(count, fail_fn) fail_fn(count)
In anycase, if there were a fastpath, that would at least have an ACQUIRE barrier (unless you set ->owner it before it or something weird). But this isn't the case, so debug should be safe afaict.
Thanks, Davidlohr
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