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[PATCH 3/3] coredump: zap_threads() must skip kernel threads

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From: Oleg Nesterov <oleg@...>
To: Andrew Morton <akpm@...>
Cc: Eric W. Biederman <ebiederm@...>, Ingo Molnar <mingo@...>, Linus Torvalds <torvalds@...>, Roland McGrath <roland@...>, <linux-kernel@...>
Subject: [PATCH 3/3] coredump: zap_threads() must skip kernel threads
Date: Sunday, June 1, 2008 - 11:30 am

The main loop in zap_threads() must skip kthreads which may use the same mm.
Otherwise we "kill" this thread erroneously (for example, it can not fork or
exec after that), and the coredumping task stucks in the TASK_UNINTERRUPTIBLE
state forever because of the wrong ->core_waiters count.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- 26-rc2/fs/exec.c~3_CD_FIX_RACE_USE_MM	2008-05-31 20:05:21.000000000 +0400
+++ 26-rc2/fs/exec.c	2008-06-01 19:04:39.000000000 +0400
@@ -1568,11 +1568,13 @@ static inline int zap_threads(struct tas
 	for_each_process(g) {
 		if (g == tsk->group_leader)
 			continue;
+		if (g->flags & PF_KTHREAD)
+			continue;
 
 		p = g;
 		do {
 			if (p->mm) {
-				if (p->mm == mm) {
+				if (unlikely(p->mm == mm)) {
 					lock_task_sighand(p, &flags);
 					zap_process(p);
 					unlock_task_sighand(p, &flags);

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Messages in current thread:
[PATCH 3/3] coredump: zap_threads() must skip kernel threads, Oleg Nesterov, (Sun Jun 1, 11:30 am)
Re: [PATCH 3/3] coredump: zap_threads() must skip kernel thr..., Andrew Morton, (Tue Jun 3, 5:15 pm)
Re: [PATCH 3/3] coredump: zap_threads() must skip kernel thr..., Roland McGrath, (Tue Jun 3, 5:49 pm)
Re: [PATCH 3/3] coredump: zap_threads() must skip kernel thr..., Andrew Morton, (Wed Jun 4, 3:57 am)