linux-kernel - [PATCH] signals: microoptimize the usage of ->curr

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Date:	Fri, 7 Mar 2008 14:57:09 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Roland McGrath <roland@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] signals: microoptimize the usage of ->curr_target

Suggested by Roland McGrath.

Initialize signal->curr_target in copy_signal(). This way ->curr_target is
never == NULL, we can kill the check in __group_complete_signal's hot path.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- 25/kernel/fork.c~4_CURR_TASK	2008-02-17 23:40:09.000000000 +0300
+++ 25/kernel/fork.c	2008-03-07 14:50:52.000000000 +0300
@@ -902,7 +902,7 @@ static int copy_signal(unsigned long clo
 	sig->group_exit_code = 0;
 	sig->group_exit_task = NULL;
 	sig->group_stop_count = 0;
-	sig->curr_target = NULL;
+	sig->curr_target = tsk;
 	init_sigpending(&sig->shared_pending);
 	INIT_LIST_HEAD(&sig->posix_timers);
 
--- 25/kernel/signal.c~4_CURR_TASK	2008-03-07 13:59:09.000000000 +0300
+++ 25/kernel/signal.c	2008-03-07 14:51:58.000000000 +0300
@@ -863,10 +863,6 @@ __group_complete_signal(int sig, struct 
 		 * Otherwise try to find a suitable thread.
 		 */
 		t = signal->curr_target;
-		if (t == NULL)
-			/* restart balancing at this thread */
-			t = signal->curr_target = p;
-
 		while (!wants_signal(sig, t)) {
 			t = next_thread(t);
 			if (t == signal->curr_target)

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