From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 21 Oct 2015 22:03:58 +0000 (+1100)
Subject: signal: introduce kernel_signal_stop() to fix jffs2_garbage_collect_thread()
X-Git-Tag: KARO-TX6UL-2015-11-03~14^2~19
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7080397e8eaad25e44281ab3d54b93d0eab5a675;p=karo-tx-linux.git

signal: introduce kernel_signal_stop() to fix jffs2_garbage_collect_thread()

jffs2_garbage_collect_thread() can race with SIGCONT and sleep in
TASK_STOPPED state after it was already sent. Add the new helper,
kernel_signal_stop(), which does this correctly.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
index f3145fd86d86..53cc7350af33 100644
--- a/fs/jffs2/background.c
+++ b/fs/jffs2/background.c
@@ -132,8 +132,7 @@ static int jffs2_garbage_collect_thread(void *_c)
 			case SIGSTOP:
 				jffs2_dbg(1, "%s(): SIGSTOP received\n",
 					  __func__);
-				set_current_state(TASK_STOPPED);
-				schedule();
+				kernel_signal_stop();
 				break;
 
 			case SIGKILL:
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ecd9409640c6..02b63957a721 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2478,6 +2478,16 @@ static inline int kernel_dequeue_signal(siginfo_t *info)
 	return ret;
 }
 
+static inline void kernel_signal_stop(void)
+{
+	spin_lock_irq(&current->sighand->siglock);
+	if (current->jobctl & JOBCTL_STOP_DEQUEUED)
+		__set_current_state(TASK_STOPPED);
+	spin_unlock_irq(&current->sighand->siglock);
+
+	schedule();
+}
+
 extern void release_task(struct task_struct * p);
 extern int send_sig_info(int, struct siginfo *, struct task_struct *);
 extern int force_sigsegv(int, struct task_struct *);