diff options
author | Huang Ying <ying.huang@intel.com> | 2011-09-08 02:00:44 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2011-10-04 06:43:39 -0400 |
commit | a3127336b71f6833d1483c856dce91fe558dc3a9 (patch) | |
tree | c025279c450994f25661c2ab004f0be98997cf8a /include/linux/llist.h | |
parent | 2c30245c65e8ebc3080b75ce65572ab8140bad0b (diff) |
llist: Move cpu_relax() to after the cmpxchg()
If in llist_add()/etc. functions the first cmpxchg() call succeeds, it is
not necessary to use cpu_relax() before the cmpxchg(). So cpu_relax() in
a busy loop involving cmpxchg() should go after cmpxchg() instead of before
that.
This patch fixes this for all involved llist functions.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315461646-1379-4-git-send-email-ying.huang@intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/llist.h')
-rw-r--r-- | include/linux/llist.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/llist.h b/include/linux/llist.h index 65fca1cbf514..ca91875286bf 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h | |||
@@ -148,11 +148,14 @@ static inline void llist_add(struct llist_node *new, struct llist_head *head) | |||
148 | struct llist_node *entry, *old_entry; | 148 | struct llist_node *entry, *old_entry; |
149 | 149 | ||
150 | entry = head->first; | 150 | entry = head->first; |
151 | do { | 151 | for (;;) { |
152 | old_entry = entry; | 152 | old_entry = entry; |
153 | new->next = entry; | 153 | new->next = entry; |
154 | entry = cmpxchg(&head->first, old_entry, new); | ||
155 | if (entry == old_entry) | ||
156 | break; | ||
154 | cpu_relax(); | 157 | cpu_relax(); |
155 | } while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry); | 158 | } |
156 | } | 159 | } |
157 | 160 | ||
158 | /** | 161 | /** |