Date: Sat, 23 Apr 2011 11:22:49 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r220967 - head/sys/kern Message-ID: <201104231122.p3NBMnHk087354@svn.freebsd.org>
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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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