Dnia 23 paź 2014 o godz. 20:38 John Baldwin <j...@freebsd.org> napisał(a):
>> On Thursday, October 23, 2014 11:35:47 am Mateusz Guzik wrote: >> Author: mjg >> Date: Thu Oct 23 15:35:47 2014 >> New Revision: 273549 >> URL: https://svnweb.freebsd.org/changeset/base/273549 >> >> Log: >> Avoid taking the lock in selfdfree when not needed. >> >> Modified: >> head/sys/kern/sys_generic.c >> >> Modified: head/sys/kern/sys_generic.c > ============================================================================== >> --- head/sys/kern/sys_generic.c Thu Oct 23 15:16:40 2014 (r273548) >> +++ head/sys/kern/sys_generic.c Thu Oct 23 15:35:47 2014 (r273549) >> @@ -1600,10 +1600,11 @@ static void >> selfdfree(struct seltd *stp, struct selfd *sfp) >> { >> STAILQ_REMOVE(&stp->st_selq, sfp, selfd, sf_link); >> - mtx_lock(sfp->sf_mtx); >> - if (sfp->sf_si) >> + if (sfp->sf_si != NULL) { >> + mtx_lock(sfp->sf_mtx); >> TAILQ_REMOVE(&sfp->sf_si->si_tdlist, sfp, sf_threads); >> - mtx_unlock(sfp->sf_mtx); >> + mtx_unlock(sfp->sf_mtx); >> + } >> uma_zfree(selfd_zone, sfp); > > How do you ensure that the value you read for sf_si here is up to date? In > particular, if a thread is selecting on multiple fds and one awakens it, > another fd can invoke selwakeup() while the thread is in seltdclear(). > In that case, you might see a stale value of sf_si and not realize it is > cleared by the selwakeup() after you get the lock and you will invoke > TAILQ_REMOVE an extra time. FWIW, I've just hit a panic in selfdfree(). _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"