Date: Sat, 7 May 2011 02:00:35 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r221570 - stable/8/sys/kern Message-ID: <201105070200.p4720ZYE075925@svn.freebsd.org>
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Author: rmacklem Date: Sat May 7 02:00:35 2011 New Revision: 221570 URL: http://svn.freebsd.org/changeset/base/221570 Log: MFC: r220967 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. Modified: stable/8/sys/kern/vfs_subr.c Directory Properties: stable/8/sys/ (props changed) stable/8/sys/amd64/include/xen/ (props changed) stable/8/sys/cddl/contrib/opensolaris/ (props changed) stable/8/sys/contrib/dev/acpica/ (props changed) stable/8/sys/contrib/pf/ (props changed) Modified: stable/8/sys/kern/vfs_subr.c ============================================================================== --- stable/8/sys/kern/vfs_subr.c Sat May 7 01:05:31 2011 (r221569) +++ stable/8/sys/kern/vfs_subr.c Sat May 7 02:00:35 2011 (r221570) @@ -380,9 +380,10 @@ 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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