On Thu, Sep 08 2005, Giancarlo Formicuccia wrote:
> Hi,
> [please CC me in any reply]
> I'm not sure that dup_task_struct() must copy the fs_excl field. This can leads to
> problems if do_fork() is somehow called while fs_excl!=0.
> For example, the jffs2 code creates a kernel thread (jffs2_garbage_collect_thread)
> in a path where lock_super() is held (i.e. by do_remount_sb, during -o remount,rw).
> When the new thread expires, a badness happens (kernel/exit.c:787). This problem
> was observed by a couple of people and can be easily reproduced:
> http://lists.infradead.org/pipermail/linux-mtd/2005-August/013487.html
> http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2005-September/031109.html
>
> At first glance, I'd simply set fs_excl to 0 for every new thread in dup_task_struct:
>
> --- linux-2.6.13/kernel/fork.c 2005-08-29 01:41:01.000000000 +0200
> +++ linux-2.6.13-new/kernel/fork.c 2005-09-07 17:06:23.000000000 +0200
> @@ -173,6 +173,7 @@ static struct task_struct *dup_task_stru
> *tsk = *orig;
> tsk->thread_info = ti;
> ti->task = tsk;
> + atomic_set(&tsk->fs_excl, 0);
>
> /* One for us, one for whoever does the "release_task()" (usually parent) */
> atomic_set(&tsk->usage,2);
>
> but I've a doubt about the WARN_ON in exit.c being actually here to report these
> kernel_thread() users (like jffs2)...
>
> Any comment/suggestion?
Patch is correct, that is definitely an oversight!
Acked-by: Jens Axboe <[email protected]>
--
Jens Axboe
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