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 >> >> >> >> >> >> 2009/7/27 John Baldwin <jhb@freebsd.org>: >> >> >> > I would actually expect this to be the correct order for these two >> >> > locks.= >> >> >> =A0Can >> >> >> > you capture the output of the 'debug.witness.fullgraph' sysctl to a >> > file? >> >> >> > >> >> >> Yes, see attachment. I'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. Can >> > 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: >> > >> > { "filedesc structure", &lock_class_sx }, >> > { "ufs", &lock_class_lockmgr}, >> > { 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: >> 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 = 0, rsp = 0xffffff800001ad30, rbp = 0 --- >> >> The output of `df' and `mount' looks ok. > > Yes, this is the "real" LOR as "filedesc" -> "ufs" in the poll() case should > be the normal order. I believe this should fix it. mountcheckdirs() doesn't > need the vnodes locked, it just needs the caller to hold references on them > 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 @@ > 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); > - vput(newdp); > - VOP_UNLOCK(vp, 0); > + vrele(newdp); > if ((mp->mnt_flag & MNT_RDONLY) == 0) > error = vfs_allocate_syncvnode(mp); > vfs_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 = 0, rsp = 0xffffff800001ad30, rbp = 0 --- René
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