Date: Thu, 23 Feb 2012 11:03:11 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: stable@freebsd.org, John Baldwin <jhb@freebsd.org> Subject: Re: panic in 8.3-PRERELEASE Message-ID: <20120223090311.GA55074@deviant.kiev.zoral.com.ua> In-Reply-To: <476361430.1773817.1329954835308.JavaMail.root@erie.cs.uoguelph.ca> References: <201202221633.02170.jhb@freebsd.org> <476361430.1773817.1329954835308.JavaMail.root@erie.cs.uoguelph.ca>
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--72pTQ1Q5L511SwPT Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Feb 22, 2012 at 06:53:55PM -0500, Rick Macklem wrote: > John Baldwin wrote: > > On Wednesday, February 22, 2012 2:24:14 pm Konstantin Belousov wrote: > > > On Wed, Feb 22, 2012 at 11:29:40AM -0500, Rick Macklem wrote: > > > > Hiroki Sato wrote: > > > > > Hi, > > > > > > > > > > Just a report, but I got the following panic on an NFS server > > > > > running > > > > > 8.3-PRERELEASE: > > > > > > > > > > ----(from here)---- > > > > > pool.allbsd.org dumped core - see /var/crash/vmcore.0 > > > > > > > > > > Tue Feb 21 10:59:44 JST 2012 > > > > > > > > > > FreeBSD pool.allbsd.org 8.3-PRERELEASE FreeBSD 8.3-PRERELEASE > > > > > #7: Thu > > > > > Feb 16 19:29:19 JST 2012 > > > > > hrs@pool.allbsd.org:/usr/obj/usr/src/sys/POOL > > > > > amd64 > > > > > > > > > > panic: Assertion lock =3D=3D sq->sq_lock failed at > > > > > /usr/src/sys/kern/subr_sleepqueue.c:335 > > > > > > > > > Oops, I didn't know that mixing msleep() and tsleep() calls on the > > > > same > > > > event wasn't allowed. > > > > There are two places in the code where it did a: > > > > mtx_unlock(); > > > > tsleep(); > > > > left over from the days when it was written for OpenBSD. > > > This sequence allows to lost the wakeup which is happen right after > > > cache unlock (together with clearing the RC_WANTED flag) but before > > > the thread enters sleep state. The tsleep has a timeout so thread > > > should > > > recover in 10 seconds, but still. > > > > > > Anyway, you should use consistent outer lock for the same wchan, > > > i.e. > > > no lock (tsleep) or mtx (msleep), but not mix them. > >=20 > > Correct. > >=20 > > > > I don't think the mix would actually break anything, except that > > > > the > > > > MPASS() assertion fails, but I've cc'd jhb@ since he seems to have > > > > been > > > > the author of the sleep() stuff. > > > > > > > > Anyhow, please try the attached patch which replaces the > > > > mtx_unlock(); > > tsleep(); with > > > > msleep()s using PDROP. If the attachment gets lost, the patch is > > > > also > > here: > > > > http://people.freebsd.org/~rmacklem/tsleep.patch > > > > > > > > Thanks for reporting this, rick > > > > ps: Is mtx_lock() now preferred over msleep()? > > > What do you mean ? > >=20 > > mtx_sleep() is preferred over msleep(), but I doubt I will remove > > msleep() > > anytime soon. > >=20 > Ok, I'll redo the patch with mtx_sleep() and get one of you guys to > review it. I do not see a need in the changing to mtx_sleep, esp. if other places in nfsd use msleep(). There are more then 570 uses of msleep(9) in the kernel, and undefined number of them in third-party modules. >=20 > One question. Do you think this is serious enough to worry about for > 8.3? (Just wondering if I need to rush a patch into head with a 1 week > MFC. I realize it would still be up to re@, even if I rush it.) I think it is usual routine bugfix, which is as good to have in release as any other bugfix. 8.3 is in the stabilization period, made exactly for pushing bugfixes. --72pTQ1Q5L511SwPT Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAk9GAM8ACgkQC3+MBN1Mb4h+CQCfSo1K540I0l3aa2Lqub5e0pzI XzYAoKbnJbm/qNi7MRMWVSyWWpGrUUOn =yDow -----END PGP SIGNATURE----- --72pTQ1Q5L511SwPT--
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