[PATCH] RCU signal handling

RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked.  This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.

Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/exec.c b/fs/exec.c
index e75a9548da8e..e9650cd22a3b 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -760,7 +760,7 @@ no_thread_group:
                 spin_lock(&oldsighand->siglock);
                 spin_lock(&newsighand->siglock);
 
-                current->sighand = newsighand;
+                rcu_assign_pointer(current->sighand, newsighand);
                 recalc_sigpending();
 
                 spin_unlock(&newsighand->siglock);
@@ -768,7 +768,7 @@ no_thread_group:
                 write_unlock_irq(&tasklist_lock);
 
                 if (atomic_dec_and_test(&oldsighand->count))
-                        kmem_cache_free(sighand_cachep, oldsighand);
+                        sighand_free(oldsighand);
         }
 
         BUG_ON(!thread_group_leader(current));