1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
Subject: fs: dcache: Use cpu_chill() in trylock loops
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 07 Mar 2012 21:00:34 +0100
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.15-rt12.tar.xz
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/autofs/expire.c | 3 ++-
fs/namespace.c | 8 ++++++--
2 files changed, 8 insertions(+), 3 deletions(-)
--- a/fs/autofs/expire.c
+++ b/fs/autofs/expire.c
@@ -8,6 +8,7 @@
* option, any later version, incorporated herein by reference.
*/
+#include <linux/delay.h>
#include "autofs_i.h"
/* Check if a dentry can be expired */
@@ -153,7 +154,7 @@ 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/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>
@@ -327,8 +328,11 @@ int __mnt_want_write(struct vfsmount *m)
* incremented count after it has set MNT_WRITE_HOLD.
*/
smp_mb();
- while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
- cpu_relax();
+ while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
+ preempt_enable();
+ cpu_chill();
+ preempt_disable();
+ }
/*
* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
* be set to match its requirements. So we must not load that until
|
