[resend: restore CC list] >>> Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> 01/07/09 6:33 PM >>> >On Wed, 7 Jan 2009, Steven Rostedt wrote: >> >> What would be interesting is various benchmarks against all three. >> >> 1) no mutex spinning. >> 2) get_task_struct() implementation. >> 3) spin_or_sched implementation. > >One of the issues is that I cannot convince myself that (2) is even >necessarily correct. At least not without having all cases happen inder >the mutex spinlock - which they don't. Even with the original patch, the >uncontended cases set and cleared the owner field outside the lock. Yeah, you are right (see my last post). Without the cmpxchg trickery (*) on the owner field (like we have in -rt) with the pending bits, (2) cannot work. (*) For what its worth, I am impressed with the brilliance of the cmgxchg fast path stuff in the rtmutex code. Whoever came up with that, my hat is off to you. -Greg
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