linux-kernel - Re: Lots of bugs with current->state = TASK

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Message-ID: <Pine.LNX.4.64.1001211145480.13529@ask.diku.dk>
Date:	Thu, 21 Jan 2010 11:47:41 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors <kernel-janitors@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arch@...r.kernel.org, Greg KH <greg@...ah.com>,
	Andy Whitcroft <apw@...onical.com>
Subject: Re: Lots of bugs with current->state = TASK_*INTERRUPTIBLE

What about something like the following (drivers/macintosh/adb.c):

        add_wait_queue(&state->wait_queue, &wait);
        current->state = TASK_INTERRUPTIBLE;

	for (;;) {
	        req = state->completed;
                if (req != NULL)
                        state->completed = req->next;
                else if (atomic_read(&state->n_pending) == 0)
                        ret = -EIO;
		if (req != NULL || ret != 0)
			break;

                if (file->f_flags & O_NONBLOCK) {
                        ret = -EAGAIN;
                        break;
		}
                if (signal_pending(current)) {
                        ret = -ERESTARTSYS;
                        break;
                }
                spin_unlock_irqrestore(&state->lock, flags);
                schedule();
        	spin_lock_irqsave(&state->lock, flags);
        }

        current->state = TASK_RUNNING;
        remove_wait_queue(&state->wait_queue, &wait);

There is a call to schedule eventually after the first current->state 
assignment, but it is not right after.

thanks,
julia
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