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Subject: fs: dcache: Use cpu_chill() in trylock loops
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 07 Mar 2012 21:00:34 +0100
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>
---
fs/autofs4/autofs_i.h | 1 +
fs/autofs4/expire.c | 2 +-
fs/dcache.c | 20 ++++++++++++++++----
fs/namespace.c | 3 ++-
4 files changed, 20 insertions(+), 6 deletions(-)
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -32,6 +32,7 @@
#include <linux/sched.h>
#include <linux/mount.h>
#include <linux/namei.h>
+#include <linux/delay.h>
#include <asm/current.h>
#include <linux/uaccess.h>
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -148,7 +148,7 @@ static struct dentry *get_next_positive_
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);
--- 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>
@@ -750,6 +751,8 @@ static inline bool fast_dput(struct dent
*/
void dput(struct dentry *dentry)
{
+ struct dentry *parent;
+
if (unlikely(!dentry))
return;
@@ -788,9 +791,18 @@ void dput(struct dentry *dentry)
return;
kill_it:
- dentry = dentry_kill(dentry);
- if (dentry) {
- cond_resched();
+ parent = dentry_kill(dentry);
+ if (parent) {
+ int r;
+
+ if (parent == dentry) {
+ /* the task with the highest priority won't schedule */
+ r = cond_resched();
+ if (!r)
+ cpu_chill();
+ } else {
+ dentry = parent;
+ }
goto repeat;
}
}
@@ -2331,7 +2343,7 @@ void d_delete(struct dentry * dentry)
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;
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -14,6 +14,7 @@
#include <linux/mnt_namespace.h>
#include <linux/user_namespace.h>
#include <linux/namei.h>
+#include <linux/delay.h>
#include <linux/security.h>
#include <linux/cred.h>
#include <linux/idr.h>
@@ -358,7 +359,7 @@ 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();
}
/*
|
