Messages in this thread | | | Date | Mon, 18 Mar 2013 17:14:18 -0700 | From | Greg KH <> | Subject | Re: [PATCH] sysfs: use atomic_inc_unless_negative in sysfs_get_active |
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On Fri, Mar 08, 2013 at 04:07:27PM +0100, Maarten Lankhorst wrote: > It seems that sysfs has an interesting way of doing the same thing. > This removes the cpu_relax unfortunately, but if it's really needed, > it would be better to add this to include/linux/atomic.h to benefit > all atomic ops users. > > Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com> > ---
Tejun wrote this code originally, so I'll defer to him as to if the patch below is a valid cleanup or not.
Tejun?
> > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c > index 2fbdff6..7f968ed 100644 > --- a/fs/sysfs/dir.c > +++ b/fs/sysfs/dir.c > @@ -165,21 +165,8 @@ struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd) > if (unlikely(!sd)) > return NULL; > > - while (1) { > - int v, t; > - > - v = atomic_read(&sd->s_active); > - if (unlikely(v < 0)) > - return NULL; > - > - t = atomic_cmpxchg(&sd->s_active, v, v + 1); > - if (likely(t == v)) > - break; > - if (t < 0) > - return NULL; > - > - cpu_relax(); > - } > + if (!atomic_inc_unless_negative(&sd->s_active)) > + return NULL; > > if (likely(!ignore_lockdep(sd))) > rwsem_acquire_read(&sd->dep_map, 0, 1, _RET_IP_);
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