Re: [PATCH] Improve behaviour of Dreamcast aica ALSA driver in poor resource conditions

["Adrian McMenamin" <adrianmcmenamin@gmail.com>]

On 03/07/07, Adrian McMenamin <adrianmcmenamin@gmail.com> wrote:
> This patch stops the driver from crashing in certain situations (eg if
> the network fails when NFS mounted), please apply.

Actually, looked at this again and while the previous patch stopped
the driver from crashing it still locked the sound subsystem. This was
because INIT_WORK was being called on the same work_struct when the
device recovered from the network failure. The patch below ensures
that this does not happen and that instead, PREPARE_WORK is called.

Submitted by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Signed-off by: Adrian McMenamin <adrian@mcmen.demon.co.uk>

--- alsa-kernel/sh/aica.c	2007-06-23 15:25:55.000000000 +0100
+++ linux-2.6.21/sound/sh/aica.c	2007-07-04 00:01:23.000000000 +0100
@@ -68,6 +68,7 @@
static struct spu_work_holder {
	struct work_struct spu_dma_work;
	void *sspointer;
+	int already_started;
} spu_working;

static struct workqueue_struct *aica_queue;
@@ -319,7 +320,13 @@
	dreamcastcard = substream->pcm->private_data;
	/*  Use queue to do the heavy lifting */
	spu_working.sspointer = substream;
-	INIT_WORK(&(spu_working.spu_dma_work), run_spu_dma);
+	if (spu_working.already_started == 1) {
+		PREPARE_WORK(&(spu_working.spu_dma_work), run_spu_dma);
+	}
+	else {
+		INIT_WORK(&(spu_working.spu_dma_work), run_spu_dma);
+		spu_working.already_started = 1;
+	}
	queue_work(aica_queue, &(spu_working.spu_dma_work));
	/* Timer may already be running */
	if (unlikely(dreamcastcard->timer.data)) {
@@ -366,7 +373,9 @@
				 *substream)
{
	struct snd_card_aica *dreamcastcard = substream->pcm->private_data;
+	flush_workqueue(aica_queue);
	del_timer(&dreamcastcard->timer);
+	aica_chn_halt();
	kfree(dreamcastcard->channel);
	spu_disable();
	return 0;
@@ -402,17 +411,10 @@
static int snd_aicapcm_pcm_trigger(struct snd_pcm_substream
				   *substream, int cmd)
{
-	struct snd_card_aica *dreamcastcard;
	switch (cmd) {
	case SNDRV_PCM_TRIGGER_START:
		spu_begin_dma(substream);
		break;
-	case SNDRV_PCM_TRIGGER_STOP:
-		dreamcastcard = substream->pcm->private_data;
-		if (dreamcastcard->timer.data)
-			del_timer(&dreamcastcard->timer);
-		aica_chn_halt();
-		break;
	default:
		return -EINVAL;
	}
-
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