From: Andrea Arcangeli <andrea@suse.de>
To: linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>
Subject: one more kthread_should_stop smp race
Date: Mon, 5 Apr 2004 01:57:40 +0200 [thread overview]
Message-ID: <20040404235740.GA21069@dualathlon.random> (raw)
reviewing the patchsets between 2.6.5-rc3 and 2.6.5 I noticed another
race like in do_softirq:
---------------
PatchSet 17177
Date: 2004/03/30 19:49:13
Author: vatsa
Branch: HEAD
Tag: (none)
Log:
[PATCH] Fix obvious stupid race in do_stop
We don't set the task state to TASK_INTERRUPTIBLE _before_ checking for
kthread_should_stop in do_stop.
BKrev: 4069c129adimxhudm2NaqM222iNj9A
Members:
ChangeSet:1.17177->1.17178
kernel/stop_machine.c:1.3->1.4
Index: linux-2.5/kernel/stop_machine.c
diff -u linux-2.5/kernel/stop_machine.c:1.3
linux-2.5/kernel/stop_machine.c:1.4
--- linux-2.5/kernel/stop_machine.c:1.3 Wed Mar 10 02:03:28 2004
+++ linux-2.5/kernel/stop_machine.c Tue Mar 30 20:49:13 2004
@@ -149,10 +149,12 @@
complete(&smdata->done);
/* Wait for kthread_stop */
+ __set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
- __set_current_state(TASK_INTERRUPTIBLE);
schedule();
+ __set_current_state(TASK_INTERRUPTIBLE);
}
+ __set_current_state(TASK_RUNNING);
return ret;
}
---------------
the TASK_INTERRUPTIBLE may become visible to other cpus after the
current cpu read kthread_should_stop.
Fix:
--- x/kernel/stop_machine.c.~1~ 2004-04-04 08:09:33.000000000 +0200
+++ x/kernel/stop_machine.c 2004-04-05 01:54:00.719800824 +0200
@@ -149,10 +149,10 @@ static int do_stop(void *_smdata)
complete(&smdata->done);
/* Wait for kthread_stop */
- __set_current_state(TASK_INTERRUPTIBLE);
+ set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
schedule();
- __set_current_state(TASK_INTERRUPTIBLE);
+ set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return ret;
reply other threads:[~2004-04-04 23:57 UTC|newest]
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