From cfdc29de6c7ab89a793d2c91d4fc9248a8cab95a Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Wed, 30 Apr 2008 00:52:51 -0700
Subject: [PATCH] --- yaml --- r: 95124 b: refs/heads/master c:
 3547ff3aefbe092ca35506c60c02e2d17a4f2199 h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/kernel/signal.c | 14 +++++++++-----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index 35de8fa7d741..2d8dbc900d14 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6e65acba7ca8169e38ab55d62d52f29a75fb141f
+refs/heads/master: 3547ff3aefbe092ca35506c60c02e2d17a4f2199
diff --git a/trunk/kernel/signal.c b/trunk/kernel/signal.c
index b3dedf1f9323..13371d17358d 100644
--- a/trunk/kernel/signal.c
+++ b/trunk/kernel/signal.c
@@ -2219,6 +2219,7 @@ static int do_tkill(int tgid, int pid, int sig)
 	int error;
 	struct siginfo info;
 	struct task_struct *p;
+	unsigned long flags;
 
 	error = -ESRCH;
 	info.si_signo = sig;
@@ -2227,21 +2228,24 @@ static int do_tkill(int tgid, int pid, int sig)
 	info.si_pid = task_tgid_vnr(current);
 	info.si_uid = current->uid;
 
-	read_lock(&tasklist_lock);
+	rcu_read_lock();
 	p = find_task_by_vpid(pid);
 	if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
 		error = check_kill_permission(sig, &info, p);
 		/*
 		 * The null signal is a permissions and process existence
 		 * probe.  No signal is actually delivered.
+		 *
+		 * If lock_task_sighand() fails we pretend the task dies
+		 * after receiving the signal. The window is tiny, and the
+		 * signal is private anyway.
 		 */
-		if (!error && sig && p->sighand) {
-			spin_lock_irq(&p->sighand->siglock);
+		if (!error && sig && lock_task_sighand(p, &flags)) {
 			error = specific_send_sig_info(sig, &info, p);
-			spin_unlock_irq(&p->sighand->siglock);
+			unlock_task_sighand(p, &flags);
 		}
 	}
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 
 	return error;
 }