linux-kernel - [PATCH 7/9] um: Should hold tasklist

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Date:	Mon, 23 Apr 2012 00:09:25 -0700
From:	Anton Vorontsov <anton.vorontsov@...aro.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Mike Frysinger <vapier@...too.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Richard Weinberger <richard@....at>,
	Paul Mundt <lethal@...ux-sh.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	John Stultz <john.stultz@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	linuxppc-dev@...ts.ozlabs.org, linux-sh@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net,
	linaro-kernel@...ts.linaro.org, patches@...aro.org,
	linux-mm@...ck.org
Subject: [PATCH 7/9] um: Should hold tasklist_lock while traversing processes

Traversing the tasks requires holding tasklist_lock, otherwise it
is unsafe.

p.s. However, I'm not sure that calling os_kill_ptraced_process()
in the atomic context is correct. It seem to work, but please
take a closer look.

Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
---
 arch/um/kernel/reboot.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index 4d93dff..66d754c 100644
--- a/arch/um/kernel/reboot.c
+++ b/arch/um/kernel/reboot.c
@@ -4,6 +4,7 @@
  */
 
 #include "linux/sched.h"
+#include "linux/spinlock.h"
 #include "linux/slab.h"
 #include "kern_util.h"
 #include "os.h"
@@ -22,6 +23,7 @@ static void kill_off_processes(void)
 		struct task_struct *p;
 		int pid;
 
+		read_lock(&tasklist_lock);
 		for_each_process(p) {
 			if (p->mm == NULL)
 				continue;
@@ -29,6 +31,7 @@ static void kill_off_processes(void)
 			pid = p->mm->context.id.u.pid;
 			os_kill_ptraced_process(pid, 1);
 		}
+		read_unlock(&tasklist_lock);
 	}
 }
 
-- 
1.7.9.2

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