[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, 9 insertions, 1 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index fb8572a42297..7fe3adfa65cb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -743,6 +743,14 @@ int unshare_files(void)
 
 EXPORT_SYMBOL(unshare_files);
 
+void sighand_free_cb(struct rcu_head *rhp)
+{
+        struct sighand_struct *sp;
+
+        sp = container_of(rhp, struct sighand_struct, rcu);
+        kmem_cache_free(sighand_cachep, sp);
+}
+
 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 {
         struct sighand_struct *sig;
@@ -752,7 +760,7 @@ static inline int copy_sighand(unsigned long clone_flags, struct task_struct * t
                 return 0;
         }
         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
-        tsk->sighand = sig;
+        rcu_assign_pointer(tsk->sighand, sig);
         if (!sig)
                 return -ENOMEM;
         spin_lock_init(&sig->siglock);