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Date: Sat, 6 Jun 2015 23:16:48 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Petr Mladek <pmladek@suse.cz>
Subject: Re: [RFC PATCH 11/18] jffs2: Convert jffs2_gcd_mtd kthread into
 the iterant API
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Cc: linux-nfs@vger.kernel.org, Borislav Petkov <bp@suse.de>,
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On 06/05, Petr Mladek wrote:
>
> [*] In fact, there was a bug in the original code. It tried to process
>     a non-existing signal when the system was freezing. See the common
>     check for pending signal and freezing.

And another bug afaics:

> -			case SIGSTOP:
> -				jffs2_dbg(1, "%s(): SIGSTOP received\n",
> -					  __func__);
> -				set_current_state(TASK_STOPPED);
> -				schedule();
> -				break;

This is obviously racy, we can miss SIGCONT.

Still I personally dislike the new kthread_sigaction() API. I agree,
a couple if signal helpers for kthreads make sense. Say,

	void kthread_do_signal_stop(void)
	{
		spin_lock_irq(&curtent->sighand->siglock);
		if (current->jobctl & JOBCTL_STOP_DEQUEUED)
			__set_current_state(TASK_STOPPED);
		spin_unlock_irq(&current->sighand->siglock);

		schedule();
	}

and probably even "int kthread_signal_deque(void)".

But personally I do not think kthread_do_signal() makes a lot of sense...

Oleg.