On Fri, 1 May 2015 21:38:13 +0200 Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> drivers/md/md.c
> drivers/md/raid1.c
> drivers/md/raid5.c
>
> Hm, so I'm not super sure about the flush_signals() in
> raid1.c:make_request() AFAICS we can do direct RAID1 writes in
> raid1_unplug(). That looks unsafe ... I've Cc:-ed Neil.
>
> raid5.c seems safe: raid5_unplug() doesn't create requests directly,
> leaves it all for the mddev kthread.
Both raid1.c and raid5.c call flush_signals() in the make_request function
(in unusual circumstances).
I wanted a uninterruptible wait which didn't add to load-average. That
approach works in kernel threads...
All the calls in md.c are in a kernel thread so safe, but I'd rather have an
explicit "uninterruptible, but no load-average" wait....
I should probably change the make_request code to queue the request
somewhere rather than wait for it to be serviceable.
I'll look into that...
> In any case, it seems to me that the patch below would be justified?
> Totally untested and so. __flush_signals() not affected.
Fine by me - does seem justified.
Thanks,
NeilBrown
>
> Thanks,
>
> Ingo
>
> ---
> kernel/signal.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index d51c5ddd855c..100e30afe5d2 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -427,6 +427,10 @@ void flush_signals(struct task_struct *t)
> {
> unsigned long flags;
>
> + /* Only kthreads are allowed to destroy signals: */
> + if (WARN_ON_ONCE(!(current->flags & PF_KTHREAD)))
> + return;
> +
> spin_lock_irqsave(&t->sighand->siglock, flags);
> __flush_signals(t);
> spin_unlock_irqrestore(&t->sighand->siglock, flags);
> --
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