Author: rmacklem
Date: Sat Apr 23 11:22:48 2011
New Revision: 220967
URL: http://svn.freebsd.org/changeset/base/220967
Log:
Fix a LOR in vfs_busy() where, after msleeping, it would lock
the mutexes in the wrong order for the case where the
MBF_MNTLSTLOCK is set. I believe this did have the
potential for deadlock. For example, if multiple nfsd threads
called vfs_busyfs(), which calls vfs_busy() with MBF_MNTLSTLOCK.
Thanks go to pho for catching this during his testing.
Tested by: pho
Submitted by: kib
MFC after: 2 weeks
Modified:
head/sys/kern/vfs_subr.c
Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c Sat Apr 23 06:37:09 2011 (r220966)
+++ head/sys/kern/vfs_subr.c Sat Apr 23 11:22:48 2011 (r220967)
@@ -377,9 +377,10 @@ vfs_busy(struct mount *mp, int flags)
if (flags & MBF_MNTLSTLOCK)
mtx_unlock(&mountlist_mtx);
mp->mnt_kern_flag |= MNTK_MWAIT;
- msleep(mp, MNT_MTX(mp), PVFS, "vfs_busy", 0);
+ msleep(mp, MNT_MTX(mp), PVFS | PDROP, "vfs_busy", 0);
if (flags & MBF_MNTLSTLOCK)
mtx_lock(&mountlist_mtx);
+ MNT_ILOCK(mp);
}
if (flags & MBF_MNTLSTLOCK)
mtx_unlock(&mountlist_mtx);
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