Date: Wed, 29 Jul 2009 11:35:17 -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: <200907291135.17569.jhb@freebsd.org> In-Reply-To: <e890cae60907290820i65abae2fracbc5ab935465089@mail.gmail.com> References: <200907271400.n6RE05Rv056472@freefall.freebsd.org> <200907290742.20838.jhb@freebsd.org> <e890cae60907290820i65abae2fracbc5ab935465089@mail.gmail.com>
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On Wednesday 29 July 2009 11:20:21 am Rene Ladan wrote: > 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 note= d=20 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 (po= ll) > >> >> >> 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 th= ese=20 two > >> >> > locks.=3D > >> >> >> =A0 =3DA0Can > >> >> >> =A0> you capture the output of the 'debug.witness.fullgraph' sys= ctl=20 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_list= s[] > > array > >> > after the 'ZFS locking list' and before the spin locks list that loo= ks > > 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)=20 @ /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=20 should > > be the normal order. =A0I believe this should fix it. =A0mountcheckdirs= ()=20 doesn't > > need the vnodes locked, it just needs the caller to hold references on= =20 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 @@ > > =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_s= yncvnode(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) : Ok, try this patch as well: =2D-- //depot/projects/smpng/sys/kern/vfs_mount.c#97 +++ /home/jhb/work/p4/smpng/sys/kern/vfs_mount.c @@ -1481,6 +1481,8 @@ if (VFS_ROOT(TAILQ_FIRST(&mountlist), LK_EXCLUSIVE, &rootvnode)) panic("Cannot find root vnode"); =20 + VOP_UNLOCK(rootvnode, 0); + p =3D curthread->td_proc; FILEDESC_XLOCK(p->p_fd); =20 @@ -1496,8 +1498,6 @@ =20 FILEDESC_XUNLOCK(p->p_fd); =20 =2D VOP_UNLOCK(rootvnode, 0); =2D EVENTHANDLER_INVOKE(mountroot); } =20 =2D-=20 John Baldwin
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