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39 lines
1.1 KiB
Diff
39 lines
1.1 KiB
Diff
Subject: fs: namespace: Use cpu_chill() in trylock loops
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 07 Mar 2012 21:00:34 +0100
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Retry loops on RT might loop forever when the modifying side was
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preempted. Use cpu_chill() instead of cpu_relax() to let the system
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make progress.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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fs/namespace.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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--- a/fs/namespace.c
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+++ b/fs/namespace.c
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@@ -14,6 +14,7 @@
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#include <linux/mnt_namespace.h>
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#include <linux/user_namespace.h>
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#include <linux/namei.h>
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+#include <linux/hrtimer.h>
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#include <linux/security.h>
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#include <linux/cred.h>
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#include <linux/idr.h>
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@@ -321,8 +322,11 @@ int __mnt_want_write(struct vfsmount *m)
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* incremented count after it has set MNT_WRITE_HOLD.
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*/
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smp_mb();
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- while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
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- cpu_relax();
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+ while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
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+ preempt_enable();
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+ cpu_chill();
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+ preempt_disable();
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+ }
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/*
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* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
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* be set to match its requirements. So we must not load that until
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