Date: Thu, 16 Sep 2004 19:22:49 -0700 From: Nate Lawson <nate@root.org> To: John Baldwin <jhb@FreeBSD.org> Cc: "M. Warner Losh" <imp@bsdimp.com> Subject: Re: cvs commit: src/sys/dev/md md.c Message-ID: <414A4A79.8060101@root.org> In-Reply-To: <200409162152.41670.jhb@FreeBSD.org> References: <20040916204321.GE30151@darkness.comp.waw.pl> <414A109E.4080601@samsco.org> <20040916.185915.35504747.imp@bsdimp.com> <200409162152.41670.jhb@FreeBSD.org>
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John Baldwin wrote: > On Thursday 16 September 2004 08:59 pm, M. Warner Losh wrote: > >>In message: <414A109E.4080601@samsco.org> >> >> Scott Long <scottl@samsco.org> writes: >>: Or just use a semaphore. >> >>Or a condition variable. > > > That doesn't help, a condition variable doesn't have state like a semaphore. > The correct fix is to do this: > > thread A > ---------- > mtx_lock(); > adjust_state(); > mtx_unlock(); > wakeup(); > > thread B > --------- > mtx_lock(); > while (state_still_needs_sleep()) > msleep(...) > mtx_unlock() > > Proving that there is no race is left as an exercise to the reader. :) Isn't this exactly what I said? -Nate
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