Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  signal: align __lock_task_sighand() irq disabling and RCU
  softirq,rcu: Inform RCU of irq_exit() activity
  sched: Add irq_{enter,exit}() to scheduler_ipi()
  rcu: protect __rcu_read_unlock() against scheduler-using irq handlers
  rcu: Streamline code produced by __rcu_read_unlock()
  rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special
  rcu: decrease rcu_report_exp_rnp coupling with scheduler

1 files changed, 13 insertions, 6 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index ff7678603328..415d85d6f6c6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1178,18 +1178,25 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
 {
         struct sighand_struct *sighand;
 
-        rcu_read_lock();
         for (;;) {
+                local_irq_save(*flags);
+                rcu_read_lock();
                 sighand = rcu_dereference(tsk->sighand);
-                if (unlikely(sighand == NULL))
+                if (unlikely(sighand == NULL)) {
+                        rcu_read_unlock();
+                        local_irq_restore(*flags);
                         break;
+                }
 
-                spin_lock_irqsave(&sighand->siglock, *flags);
-                if (likely(sighand == tsk->sighand))
+                spin_lock(&sighand->siglock);
+                if (likely(sighand == tsk->sighand)) {
+                        rcu_read_unlock();
                         break;
-                spin_unlock_irqrestore(&sighand->siglock, *flags);
+                }
+                spin_unlock(&sighand->siglock);
+                rcu_read_unlock();
+                local_irq_restore(*flags);
         }
-        rcu_read_unlock();
 
         return sighand;
 }