[PATCH 6/6] get_utrace_lock: do not check EXIT_DEAD

[Oleg Nesterov]

get_utrace_lock() checks ->state != EXIT_DEAD to make sure it safe
to use ->utrace. This is unneeded since ->utrace was embedded into
task_struct. If we can read ->state, we can read ->utrace as well.

Signed-off-by: Oleg Nesterov <oleg at redhat.com>
----

 kernel/utrace.c |   26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

--- __UTRACE/kernel/utrace.c~6_GET_UTRACE_LOCK	2009-07-31 02:35:50.000000000 +0200
+++ __UTRACE/kernel/utrace.c	2009-07-31 02:47:42.000000000 +0200
@@ -493,27 +493,17 @@ static struct utrace *get_utrace_lock(st
 	}
 
 	utrace = &target->utrace;
-	if (unlikely(target->exit_state == EXIT_DEAD)) {
+	spin_lock(&utrace->lock);
+	if (unlikely(!engine->ops) ||
+	    unlikely(engine->ops == &utrace_detached_ops)) {
 		/*
-		 * If all engines detached already, utrace is clear.
-		 * Otherwise, we're called after utrace_release_task might
-		 * have started.  A call to this engine's report_reap
-		 * callback might already be in progress.
+		 * By the time we got the utrace lock,
+		 * it had been reaped or detached already.
 		 */
+		spin_unlock(&utrace->lock);
 		utrace = ERR_PTR(-ESRCH);
-	} else {
-		spin_lock(&utrace->lock);
-		if (unlikely(!engine->ops) ||
-		    unlikely(engine->ops == &utrace_detached_ops)) {
-			/*
-			 * By the time we got the utrace lock,
-			 * it had been reaped or detached already.
-			 */
-			spin_unlock(&utrace->lock);
-			utrace = ERR_PTR(-ESRCH);
-			if (!attached && engine->ops == &utrace_detached_ops)
-				utrace = ERR_PTR(-ERESTARTSYS);
-		}
+		if (!attached && engine->ops == &utrace_detached_ops)
+			utrace = ERR_PTR(-ERESTARTSYS);
 	}
 	rcu_read_unlock();