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From: Andriy Gapon <avg@FreeBSD.org>
Date: Sat, 10 Nov 2012 12:06:24 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r242858 -
 stable/9/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
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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);
 }