rt-patches/0168-fs-dcache-Use-cpu_chill-in-trylock-loops.patch

   1 From eb48fbfdea1555dbca8763fe221d42659b5f3113 Mon Sep 17 00:00:00 2001
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Wed, 7 Mar 2012 21:00:34 +0100
   4 Subject: [PATCH 168/366] fs: dcache: Use cpu_chill() in trylock loops
   5
   6 Retry loops on RT might loop forever when the modifying side was
   7 preempted. Use cpu_chill() instead of cpu_relax() to let the system
   8 make progress.
   9
  10 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  11 ---
  12  fs/autofs4/autofs_i.h |  1 +
  13  fs/autofs4/expire.c   |  2 +-
  14  fs/dcache.c           | 10 ++++++++--
  15  fs/namespace.c        |  3 ++-
  16  4 files changed, 12 insertions(+), 4 deletions(-)
  17
  18 diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
  19 index 502d389..05af8d3 100644
  20 --- a/fs/autofs4/autofs_i.h
  21 +++ b/fs/autofs4/autofs_i.h
  22 @@ -34,6 +34,7 @@
  23  #include <linux/sched.h>
  24  #include <linux/mount.h>
  25  #include <linux/namei.h>
  26 +#include <linux/delay.h>
  27  #include <asm/current.h>
  28  #include <asm/uaccess.h>
  29
  30 diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
  31 index 7a5a598..d08bcdc 100644
  32 --- a/fs/autofs4/expire.c
  33 +++ b/fs/autofs4/expire.c
  34 @@ -150,7 +150,7 @@ again:
  35                         parent = p->d_parent;
  36                         if (!spin_trylock(&parent->d_lock)) {
  37                                 spin_unlock(&p->d_lock);
  38 -                               cpu_relax();
  39 +                               cpu_chill();
  40                                 goto relock;
  41                         }
  42                         spin_unlock(&p->d_lock);
  43 diff --git a/fs/dcache.c b/fs/dcache.c
  44 index 9e50999..2ee5a8e6 100644
  45 --- a/fs/dcache.c
  46 +++ b/fs/dcache.c
  47 @@ -19,6 +19,7 @@
  48  #include <linux/mm.h>
  49  #include <linux/fs.h>
  50  #include <linux/fsnotify.h>
  51 +#include <linux/delay.h>
  52  #include <linux/slab.h>
  53  #include <linux/init.h>
  54  #include <linux/hash.h>
  55 @@ -785,7 +786,12 @@ repeat:
  56  kill_it:
  57         dentry = dentry_kill(dentry);
  58         if (dentry) {
  59 -               cond_resched();
  60 +               int r;
  61 +
  62 +               /* the task with the highest priority won't schedule */
  63 +               r = cond_resched();
  64 +               if (!r)
  65 +                       cpu_chill();
  66                 goto repeat;
  67         }
  68  }
  69 @@ -2394,7 +2400,7 @@ again:
  70         if (dentry->d_lockref.count == 1) {
  71                 if (!spin_trylock(&inode->i_lock)) {
  72                         spin_unlock(&dentry->d_lock);
  73 -                       cpu_relax();
  74 +                       cpu_chill();
  75                         goto again;
  76                 }
  77                 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
  78 diff --git a/fs/namespace.c b/fs/namespace.c
  79 index 97f7f9f..1f3725b 100644
  80 --- a/fs/namespace.c
  81 +++ b/fs/namespace.c
  82 @@ -14,6 +14,7 @@
  83  #include <linux/mnt_namespace.h>
  84  #include <linux/user_namespace.h>
  85  #include <linux/namei.h>
  86 +#include <linux/delay.h>
  87  #include <linux/security.h>
  88  #include <linux/idr.h>
  89  #include <linux/init.h>                /* init_rootfs */
  90 @@ -355,7 +356,7 @@ int __mnt_want_write(struct vfsmount *m)
  91         smp_mb();
  92         while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
  93                 preempt_enable();
  94 -               cpu_relax();
  95 +               cpu_chill();
  96                 preempt_disable();
  97         }
  98         /*
  99 --
 100 1.9.1
 101