ahci: improve and limit spurious interrupt messages, take#3

[powerpc.git] / kernel / sys.c

diff --git a/kernel/sys.c b/kernel/sys.c
index 4f9d23a..6e2101d 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -323,11 +323,18 @@ EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
 int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
                unsigned long val, void *v)
 {
-       int ret;
+       int ret = NOTIFY_DONE;
 
-       down_read(&nh->rwsem);
-       ret = notifier_call_chain(&nh->head, val, v);
-       up_read(&nh->rwsem);
+       /*
+        * We check the head outside the lock, but if this access is
+        * racy then it does not matter what the result of the test
+        * is, we re-check the list after having taken the lock anyway:
+        */
+       if (rcu_dereference(nh->head)) {
+               down_read(&nh->rwsem);
+               ret = notifier_call_chain(&nh->head, val, v);
+               up_read(&nh->rwsem);
+       }
        return ret;
 }
 
@@ -1397,16 +1404,13 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
                goto out;
 
        if (pgid != pid) {
-               struct task_struct *p;
+               struct task_struct *g =
+                       find_task_by_pid_type(PIDTYPE_PGID, pgid);
 
-               do_each_task_pid(pgid, PIDTYPE_PGID, p) {
-                       if (process_session(p) == process_session(group_leader))
-                               goto ok_pgid;
-               } while_each_task_pid(pgid, PIDTYPE_PGID, p);
-               goto out;
+               if (!g || process_session(g) != process_session(group_leader))
+                       goto out;
        }
 
-ok_pgid:
        err = security_task_setpgid(p, pgid);
        if (err)
                goto out;