svn commit: r242858 - stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Andriy Gapon]

Author: avg
Date: Sat Nov 10 12:06:24 2012
New Revision: 242858
URL: http://svnweb.freebsd.org/changeset/base/242858

Log:
  MFC r241773: zfs: wait in arc_lowmem only if curproc == pageproc

Modified:
  stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/cddl/contrib/opensolaris/   (props changed)

Modified: stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
==============================================================================
--- stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c	Sat Nov 10 12:04:22 2012	(r242857)
+++ stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c	Sat Nov 10 12:06:24 2012	(r242858)
@@ -3718,8 +3718,16 @@ arc_lowmem(void *arg __unused, int howto
 	mutex_enter(&arc_reclaim_thr_lock);
 	needfree = 1;
 	cv_signal(&arc_reclaim_thr_cv);
-	while (needfree)
-		msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
+
+	/*
+	 * It is unsafe to block here in arbitrary threads, because we can come
+	 * here from ARC itself and may hold ARC locks and thus risk a deadlock
+	 * with ARC reclaim thread.
+	 */
+	if (curproc == pageproc) {
+		while (needfree)
+			msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
+	}
 	mutex_exit(&arc_reclaim_thr_lock);
 	mutex_exit(&arc_lowmem_lock);
 }