| Subject: fs: namespace: 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/namespace.c | 8 ++++++-- |
| 1 file changed, 6 insertions(+), 2 deletions(-) |
| |
| --- 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> |
| @@ -321,8 +322,11 @@ 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 |
