RE: [PATCH] mm : Avoid candidate task is equal to current task

[Peter Chiang]

Is it possible  before exit_mm() set tsk->mm to NULL, tsk->mm has already been NULL ?

-----Original Message-----
From: Peter Chiang 
Sent: Wednesday, April 16, 2014 8:31 PM
To: Peter Chiang; ccross@xxxxxxxxxxx; lizefan@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; oleg@xxxxxxxxxx; tj@xxxxxxxxxx; pavel@xxxxxx; ebiederm@xxxxxxxxxxxx; guillaume@xxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Subject: RE: [PATCH] mm : Avoid candidate task is equal to current task

mm_update_next_owner() call from exit_mm() , and exit_mm()  change tsk->mm to NULL If p==c , It seems to be  impossible that mm == c->mm  (tsk->mm) . Because mm is non-NULL and  c->mm is NULL . 


-----Original Message-----
From: Peter Chiang [mailto:pchiang@xxxxxxxxxx]
Sent: Wednesday, April 16, 2014 11:03 AM
To: ccross@xxxxxxxxxxx; Peter Chiang; lizefan@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; oleg@xxxxxxxxxx; tj@xxxxxxxxxx; pavel@xxxxxx; ebiederm@xxxxxxxxxxxx; guillaume@xxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH] mm : Avoid candidate task is equal to current task

From: pchiang <pchiang@xxxxxxxxxx>

Fix kernel panic when finding a new owner for the mm and the new owner is equal to current onwer

Signed-off-by: pchiang <pchiang@xxxxxxxxxx>
---
 kernel/exit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/exit.c b/kernel/exit.c index 6ed6a1d..aa98422 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -399,7 +399,7 @@ retry:
 	 * here often
 	 */
 	do_each_thread(g, c) {
-		if (c->mm == mm)
+		if ((c != p) && (c->mm == mm))
 			goto assign_new_owner;
 	} while_each_thread(g, c);
 
--
1.8.1.5

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