From b4e35a44d3c268150f3803121e1d9ca1e5e9f998 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 7 Mar 2012 21:00:34 +0100
Subject: fs: dcache: Use cpu_chill() in trylock loops

Retry loops on RT might loop forever when the modifying side was
preempted. Use cpu_chill() instead of cpu_relax() to let the system
make progress.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable-rt@vger.kernel.org

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 3f1128b..c2ed9c4 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -34,6 +34,7 @@
 #include <linux/sched.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
+#include <linux/delay.h>
 #include <asm/current.h>
 #include <asm/uaccess.h>
 
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 3d9d3f5..b422ad6 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -157,7 +157,7 @@ again:
 			parent = p->d_parent;
 			if (!spin_trylock(&parent->d_lock)) {
 				spin_unlock(&p->d_lock);
-				cpu_relax();
+				cpu_chill();
 				goto relock;
 			}
 			spin_unlock(&p->d_lock);
diff --git a/fs/dcache.c b/fs/dcache.c
index 4021e01..ae2a83e 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/fsnotify.h>
+#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/hash.h>
@@ -554,7 +555,7 @@ dentry_kill(struct dentry *dentry, int unlock_on_failure)
 relock:
 		if (unlock_on_failure) {
 			spin_unlock(&dentry->d_lock);
-			cpu_relax();
+			cpu_chill();
 		}
 		return dentry; /* try again with same dentry */
 	}
@@ -2391,7 +2392,7 @@ again:
 	if (dentry->d_lockref.count == 1) {
 		if (!spin_trylock(&inode->i_lock)) {
 			spin_unlock(&dentry->d_lock);
-			cpu_relax();
+			cpu_chill();
 			goto again;
 		}
 		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
diff --git a/fs/namespace.c b/fs/namespace.c
index 6ed0fb1..22cbfab 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -23,6 +23,7 @@
 #include <linux/uaccess.h>
 #include <linux/proc_ns.h>
 #include <linux/magic.h>
+#include <linux/delay.h>
 #include "pnode.h"
 #include "internal.h"
 
@@ -317,7 +318,7 @@ int __mnt_want_write(struct vfsmount *m)
 	smp_mb();
 	while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
 		preempt_enable();
-		cpu_relax();
+		cpu_chill();
 		preempt_disable();
 	}
 	/*
-- 
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