Date: Wed, 29 Jul 2009 17:20:21 +0200 From: Rene Ladan <rene@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: kern/136945: [ufs] [lor] filedesc structure/ufs (poll) Message-ID: <e890cae60907290820i65abae2fracbc5ab935465089@mail.gmail.com> In-Reply-To: <200907290742.20838.jhb@freebsd.org> References: <200907271400.n6RE05Rv056472@freefall.freebsd.org> <200907281038.30277.jhb@freebsd.org> <e890cae60907290252n409c1503g9a15cfe0de43a845@mail.gmail.com> <200907290742.20838.jhb@freebsd.org>
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2009/7/29 John Baldwin <jhb@freebsd.org>: > 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 thes= e two >> >> > locks.=3D >> >> >> =A0 =3DA0Can >> >> >> =A0> you capture the output of the 'debug.witness.fullgraph' sysct= l 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 > 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 > point. =A0Can >> > you patch sys/kern/subr_witness.c to add a section to the order_lists[= ] > array >> > after the 'ZFS locking list' and before the spin locks list that looks > 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. >> >> But now a new LOR (according to the LOR page) seems pop up: >> Trying to mount root from ufs:/dev/ad0s1a >> lock order reversal: >> =A01st 0xffffff0002a4ad80 ufs (ufs) @ /usr/src/sys/ufs/ffs/ffs_vfsops.c:= 1465 >> =A02nd 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 --- >> >> The output of `df' and `mount' looks ok. > > Yes, this is the "real" LOR as "filedesc" -> "ufs" in the poll() case sho= uld > be the normal order. =A0I believe this should fix it. =A0mountcheckdirs()= doesn't > need the vnodes locked, it just needs the caller to hold references on th= em > so they aren't recycled: > > --- //depot/projects/smpng/sys/kern/vfs_mount.c#96 > +++ /home/jhb/work/p4/smpng/sys/kern/vfs_mount.c > @@ -1069,9 +1069,10 @@ > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0vfs_event_signal(NULL, VQ_MOUNT, 0); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (VFS_ROOT(mp, LK_EXCLUSIVE, &newdp)) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0panic("mount: lost mount")= ; > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 VOP_UNLOCK(newdp, 0); > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 VOP_UNLOCK(vp, 0); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0mountcheckdirs(vp, newdp); > - =A0 =A0 =A0 =A0 =A0 =A0 =A0 vput(newdp); > - =A0 =A0 =A0 =A0 =A0 =A0 =A0 VOP_UNLOCK(vp, 0); > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 vrele(newdp); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if ((mp->mnt_flag & MNT_RDONLY) =3D=3D 0) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0error =3D vfs_allocate_syn= cvnode(mp); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0vfs_unbusy(mp); > The LOR is still present, but at a different place without the mountcheckdirs() call (not on the LOR page either) : Trying to mount root from ufs:/dev/ad0s1a lock order reversal: 1st 0xffffff0002a4ad80 ufs (ufs) @ /usr/src/sys/kern/vfs_subr.c:2083 2nd 0xffffff000233f048 filedesc structure (filedesc structure) @ /usr/src/sys/kern/vfs_mount.c:1485 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 set_rootvnode() at set_rootvnode+0x57 vfs_mountroot_try() at vfs_mountroot_try+0x371 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 --- Ren=E9
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