commit b8534d7bd89df0cd41cd47bcd6733a05ea9a691a
author Oleg Nesterov <oleg@tv-sign.ru> Sat Oct 28 10:38:53 2006 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> Sat Oct 28 11:30:54 2006 -0700
tree c4650f417d7f05a9c645d6a0b1f64405ec4c8a39
parent 17b02695b254aa2ef0e53df9c8e6548f86e66a9d

[PATCH] taskstats: kill ->taskstats_lock in favor of ->siglock

signal_struct is (mostly) protected by ->sighand->siglock, I think we don't
need ->taskstats_lock to protect ->stats.  This also allows us to simplify the
locking in fill_tgid().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/taskstats.c

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 9aeee51..b2efda9 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -241,11 +241,11 @@
 	tsk = first;
 	read_lock(&tasklist_lock);
 	/* Start with stats from dead tasks */
-	if (first->signal) {
-		spin_lock_irqsave(&first->signal->stats_lock, flags);
+	if (first->sighand) {
+		spin_lock_irqsave(&first->sighand->siglock, flags);
 		if (first->signal->stats)
 			memcpy(stats, first->signal->stats, sizeof(*stats));
-		spin_unlock_irqrestore(&first->signal->stats_lock, flags);
+		spin_unlock_irqrestore(&first->sighand->siglock, flags);
 	}
 
 	do {
@@ -276,7 +276,7 @@
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&tsk->signal->stats_lock, flags);
+	spin_lock_irqsave(&tsk->sighand->siglock, flags);
 	if (!tsk->signal->stats)
 		goto ret;
 
@@ -288,7 +288,7 @@
 	 */
 	delayacct_add_tsk(tsk->signal->stats, tsk);
 ret:
-	spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
+	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 	return;
 }
 
@@ -464,15 +464,10 @@
 	size_t size;
 	int is_thread_group;
 	struct nlattr *na;
-	unsigned long flags;
 
 	if (!family_registered || !tidstats)
 		return;
 
-	spin_lock_irqsave(&tsk->signal->stats_lock, flags);
-	is_thread_group = tsk->signal->stats ? 1 : 0;
-	spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
-
 	rc = 0;
 	/*
 	 * Size includes space for nested attributes
@@ -480,6 +475,7 @@
 	size = nla_total_size(sizeof(u32)) +
 		nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
 
+	is_thread_group = (tsk->signal->stats != NULL);
 	if (is_thread_group)
 		size = 2 * size;	/* PID + STATS + TGID + STATS */