Date: Tue, 1 Feb 2011 09:50:29 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-stable@freebsd.org Cc: John Hickey <jjh@deterlab.net> Subject: Re: nfsd hung on ufs vnode lock Message-ID: <201102010950.29346.jhb@freebsd.org> In-Reply-To: <20110131222924.GF7923@deterlab.net> References: <C36EE8BD-D906-4B46-AD96-3916FFBAD254@deterlab.net> <201101311200.29897.jhb@freebsd.org> <20110131222924.GF7923@deterlab.net>
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On Monday, January 31, 2011 5:29:24 pm John Hickey wrote: > On Mon, Jan 31, 2011 at 12:00:29PM -0500, John Baldwin wrote: > (kgdb) vprint vp > 0xd417633c: tag none, type VBAD > usecount 0, writecount 0, refcount 1 mountedhere 0x0 > flags (VI_DOOMED) > lock type ufs: UNLOCKED with 1 pending > (kgdb) Ok, this looks exactly like the bug I fixed in the two revisions below. > > There's a chance though you are tripping over the bug fixed by these two > > changes: > > I should be able to sync up with 7.4 without much pain in a few days. > > > Author: jhb > > Date: Fri Jul 16 20:23:24 2010 > > New Revision: 210173 > > URL: http://svn.freebsd.org/changeset/base/210173 > > > > Log: > > When the MNTK_EXTENDED_SHARED mount option was added, some filesystems were > > changed to defer the setting of VN_LOCK_ASHARE() (which clears LK_NOSHARE > > in the vnode lock's flags) until after they had determined if the vnode was > > a FIFO. This occurs after the vnode has been inserted into a VFS hash or > > some similar table, so it is possible for another thread to find this vnode > > via vget() on an i-node number and block on the vnode lock. If the lockmgr > > interlock (vnode interlock for vnode locks) is not held when clearing the > > LK_NOSHARE flag, then the lk_flags field can be clobbered. As a result > > the thread blocked on the vnode lock may never get woken up. Fix this by > > holding the vnode interlock while modifying the lock flags in this case. > > > > The softupdates code also toggles LK_NOSHARE in one function to close a > > race with snapshots. Fix this code to grab the interlock while fiddling > > with lk_flags. > > > > Author: jhb > > Date: Fri Aug 20 20:58:57 2010 > > New Revision: 211533 > > URL: http://svn.freebsd.org/changeset/base/211533 > > > > Log: > > Revert 210173 as it did not properly fix the bug. It assumed that the > > VI_LOCK() for a given vnode was used as the internal interlock for that > > vnode's v_lock lockmgr lock. This is not the case. Instead, add dedicated > > routines to toggle the LK_NOSHARE and LK_CANRECURSE flags. These routines > > lock the lockmgr lock's internal interlock to synchronize the updates to > > the flags member with other threads attempting to acquire the lock. The > > VN_LOCK_A*() macros now invoke these routines, and the softupdates code > > uses these routines to temporarly enable recursion on buffer locks. > > > > Reviewed by: kib -- John Baldwin
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