From: Keir Fraser <keir.fraser@citrix.com>
Date: Tue, 20 Apr 2010 13:32:53 +0000 (+0100)
Subject: tasklet: Add lock-free exit path from do_tasklet() when no work to do.
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~12334
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success/%22http:/www.example.com/cgi/success?a=commitdiff_plain;h=3cd0ba42d51b8bb2b8e534b52c7d8f10e1676868;p=xen.git

tasklet: Add lock-free exit path from do_tasklet() when no work to do.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
---

diff --git a/xen/common/tasklet.c b/xen/common/tasklet.c
index 05665ebc5d..e2109770ad 100644
--- a/xen/common/tasklet.c
+++ b/xen/common/tasklet.c
@@ -60,9 +60,12 @@ void do_tasklet(void)
     struct list_head *list = &per_cpu(tasklet_list, cpu);
     struct tasklet *t;
 
+    if ( likely(list_empty(list)) )
+        return;
+
     spin_lock_irq(&tasklet_lock);
 
-    if ( list_empty(list) )
+    if ( unlikely(list_empty(list)) )
     {
         spin_unlock_irq(&tasklet_lock);
         return;