Messages in this thread | | | Date | Tue, 27 Dec 2005 14:15:01 +0100 | From | Ingo Molnar <> | Subject | Re: [patch 1/3] mutex subsystem: trylock |
| |
* Arjan van de Ven <arjan@infradead.org> wrote:
> > + * 1) if the exclusive store fails we fail, and > > + * > > + * 2) if the decremented value is not zero we don't even attempt the store. > > > btw I really think that 1) is wrong. trylock should do everything it > can to get the semaphore short of sleeping. Just because some > cacheline got written to (which might even be shared!) in the middle > of the atomic op is not a good enough reason to fail the trylock imho. > Going into the slowpath.. fine. But here it's a quality of > implementation issue; you COULD get the semaphore without sleeping (at > least probably, you'd have to retry to know for sure) but because > something wrote to the same cacheline as the lock... no. that's just > not good enough.. sorry.
point. I solved this in my tree by calling the generic trylock <fn> if there's an __ex_flag failure in the ARMv6 case. Should be rare (and thus the call is under unlikely()), and should thus still enable the fast implementation.
Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |