Date: Wed, 29 Jul 2009 07:42:20 -0400 From: John Baldwin <jhb@freebsd.org> To: Rene Ladan <rene@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: kern/136945: [ufs] [lor] filedesc structure/ufs (poll) Message-ID: <200907290742.20838.jhb@freebsd.org> In-Reply-To: <e890cae60907290252n409c1503g9a15cfe0de43a845@mail.gmail.com> References: <200907271400.n6RE05Rv056472@freefall.freebsd.org> <200907281038.30277.jhb@freebsd.org> <e890cae60907290252n409c1503g9a15cfe0de43a845@mail.gmail.com>
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On Wednesday 29 July 2009 5:52:24 am Rene Ladan wrote: > 2009/7/28 John Baldwin <jhb@freebsd.org>: > > On Tuesday 28 July 2009 10:03:40 am Rene Ladan wrote: > >> 2009/7/28 John Baldwin <jhb@freebsd.org>: > >> > On Monday 27 July 2009 10:00:05 am Rene Ladan wrote: > >> >> The following reply was made to PR kern/136945; it has been noted by > > GNATS. > >> >> > >> >> From: Rene Ladan <rene@freebsd.org> > >> >> To: John Baldwin <jhb@freebsd.org> > >> >> Cc: bug-followup@freebsd.org > >> >> Subject: Re: kern/136945: [ufs] [lor] filedesc structure/ufs (poll) > >> >> Date: Mon, 27 Jul 2009 15:51:15 +0200 > >> >> > >> >> =A02009/7/27 John Baldwin <jhb@freebsd.org>: > >> >> =A0> I would actually expect this to be the correct order for these= two > >> > locks.=3D > >> >> =A0 =3DA0Can > >> >> =A0> you capture the output of the 'debug.witness.fullgraph' sysctl= to a > > file? > >> >> =A0> > >> >> =A0Yes, see attachment. =A0I'm still running the same 8.0-BETA2. > >> > > >> > Hmm, the attachment was eaten by a grue, can you post the file=20 somewhere? > >> > > >> Yes, see ftp://rene-ladan.nl/pub/freebsd/kern_136945.txt > > > > Ok, it looks like it did encounter a UFS -> filedesc order at some=20 point. =A0Can > > you patch sys/kern/subr_witness.c to add a section to the order_lists[]= =20 array > > after the 'ZFS locking list' and before the spin locks list that looks= =20 like > > this: > > > > =A0 =A0 =A0 =A0{ "filedesc structure", &lock_class_sx }, > > =A0 =A0 =A0 =A0{ "ufs", &lock_class_lockmgr}, > > =A0 =A0 =A0 =A0{ NULL, NULL }, > > > The LOR seems to be gone, previously it showed up only once right > after booting the system. >=20 > But now a new LOR (according to the LOR page) seems pop up: > Trying to mount root from ufs:/dev/ad0s1a > lock order reversal: > 1st 0xffffff0002a4ad80 ufs (ufs) @ /usr/src/sys/ufs/ffs/ffs_vfsops.c:1465 > 2nd 0xffffff0002b29a48 filedesc structure (filedesc structure) @ > /usr/src/sys/kern/kern_descrip.c:2478 > KDB: stack backtrace: > db_trace_self_wrapper() at db_trace_self_wrapper+0x2a > _witness_debugger() at _witness_debugger+0x49 > witness_checkorder() at witness_checkorder+0x7ea > _sx_xlock() at _sx_xlock+0x44 > mountcheckdirs() at mountcheckdirs+0x80 > vfs_donmount() at vfs_donmount+0xfbf > kernel_mount() at kernel_mount+0xa1 > vfs_mountroot_try() at vfs_mountroot_try+0x177 > vfs_mountroot() at vfs_mountroot+0x47d > start_init() at start_init+0x62 > fork_exit() at fork_exit+0x12a > fork_trampoline() at fork_trampoline+0xe > --- trap 0, rip =3D 0, rsp =3D 0xffffff800001ad30, rbp =3D 0 --- >=20 > The output of `df' and `mount' looks ok. Yes, this is the "real" LOR as "filedesc" -> "ufs" in the poll() case shoul= d=20 be the normal order. I believe this should fix it. mountcheckdirs() doesn= 't=20 need the vnodes locked, it just needs the caller to hold references on them= =20 so they aren't recycled: =2D-- //depot/projects/smpng/sys/kern/vfs_mount.c#96 +++ /home/jhb/work/p4/smpng/sys/kern/vfs_mount.c @@ -1069,9 +1069,10 @@ vfs_event_signal(NULL, VQ_MOUNT, 0); if (VFS_ROOT(mp, LK_EXCLUSIVE, &newdp)) panic("mount: lost mount"); + VOP_UNLOCK(newdp, 0); + VOP_UNLOCK(vp, 0); mountcheckdirs(vp, newdp); =2D vput(newdp); =2D VOP_UNLOCK(vp, 0); + vrele(newdp); if ((mp->mnt_flag & MNT_RDONLY) =3D=3D 0) error =3D vfs_allocate_syncvnode(mp); vfs_unbusy(mp); =2D-=20 John Baldwin
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