V4L/DVB (10572): Revert commit dda06a8

On Mon, 02 Feb 2009, Hartmut wrote:

This change set is wrong. The affected functions cannot be called from
an interrupt context, because they may process large buffers. In this
case, interrupts are disabled for a long time. Functions, like
dvb_dmx_swfilter_packets(), could be called only from a tasklet.

This change set does hide some strong design bugs in dm1105.c and
au0828-dvb.c.

Please revert this change set and do fix the bugs in dm1105.c and
au0828-dvb.c (and other files).

On Sun, 15 Feb 2009, Oliver Endriss wrote:

This changeset _must_ be reverted! It breaks all kernels since 2.6.27
for applications which use DVB and require a low interrupt latency.

It is a very bad idea to call the demuxer to process data buffers with
interrupts disabled!

On Mon, 16 Feb 2009, Trent Piepho wrote:

I agree, this is bad.  The demuxer is far too much work to be done with
IRQs off.  IMHO, even doing it under a spin-lock is excessive.  It should
be a mutex.  Drivers should use a work-queue to feed the demuxer.

Thank you for testing this changeset and discovering the issues on it.

Cc: Trent Piepho <xyzzy@speakeasy.org>
Cc: Hartmut <e9hack@googlemail.com>
Cc: Oliver Endriss <o.endriss@gmx.de>
Cc: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/dvb-core/dmxdev.c

@@ -364,16 +364,15 @@ static int dvb_dmxdev_section_callback(const u8 *buffer1, size_t buffer1_len,
 				       enum dmx_success success)
 {
 	struct dmxdev_filter *dmxdevfilter = filter->priv;
-	unsigned long flags;
 	int ret;
 
 	if (dmxdevfilter->buffer.error) {
 		wake_up(&dmxdevfilter->buffer.queue);
 		return 0;
 	}
-	spin_lock_irqsave(&dmxdevfilter->dev->lock, flags);
+	spin_lock(&dmxdevfilter->dev->lock);
 	if (dmxdevfilter->state != DMXDEV_STATE_GO) {
-		spin_unlock_irqrestore(&dmxdevfilter->dev->lock, flags);
+		spin_unlock(&dmxdevfilter->dev->lock);
 		return 0;
 	}
 	del_timer(&dmxdevfilter->timer);
@@ -392,7 +391,7 @@ static int dvb_dmxdev_section_callback(const u8 *buffer1, size_t buffer1_len,
 	}
 	if (dmxdevfilter->params.sec.flags & DMX_ONESHOT)
 		dmxdevfilter->state = DMXDEV_STATE_DONE;
-	spin_unlock_irqrestore(&dmxdevfilter->dev->lock, flags);
+	spin_unlock(&dmxdevfilter->dev->lock);
 	wake_up(&dmxdevfilter->buffer.queue);
 	return 0;
 }
@@ -404,12 +403,11 @@ static int dvb_dmxdev_ts_callback(const u8 *buffer1, size_t buffer1_len,
 {
 	struct dmxdev_filter *dmxdevfilter = feed->priv;
 	struct dvb_ringbuffer *buffer;
-	unsigned long flags;
 	int ret;
 
-	spin_lock_irqsave(&dmxdevfilter->dev->lock, flags);
+	spin_lock(&dmxdevfilter->dev->lock);
 	if (dmxdevfilter->params.pes.output == DMX_OUT_DECODER) {
-		spin_unlock_irqrestore(&dmxdevfilter->dev->lock, flags);
+		spin_unlock(&dmxdevfilter->dev->lock);
 		return 0;
 	}
 
@@ -419,7 +417,7 @@ static int dvb_dmxdev_ts_callback(const u8 *buffer1, size_t buffer1_len,
 	else
 		buffer = &dmxdevfilter->dev->dvr_buffer;
 	if (buffer->error) {
-		spin_unlock_irqrestore(&dmxdevfilter->dev->lock, flags);
+		spin_unlock(&dmxdevfilter->dev->lock);
 		wake_up(&buffer->queue);
 		return 0;
 	}
@@ -430,7 +428,7 @@ static int dvb_dmxdev_ts_callback(const u8 *buffer1, size_t buffer1_len,
 		dvb_ringbuffer_flush(buffer);
 		buffer->error = ret;
 	}
-	spin_unlock_irqrestore(&dmxdevfilter->dev->lock, flags);
+	spin_unlock(&dmxdevfilter->dev->lock);
 	wake_up(&buffer->queue);
 	return 0;
 }

drivers/media/dvb/dvb-core/dvb_demux.c

@@ -399,27 +399,24 @@ static void dvb_dmx_swfilter_packet(struct dvb_demux *demux, const u8 *buf)
 void dvb_dmx_swfilter_packets(struct dvb_demux *demux, const u8 *buf,
 			      size_t count)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&demux->lock, flags);
+	spin_lock(&demux->lock);
 
 	while (count--) {
 		if (buf[0] == 0x47)
 			dvb_dmx_swfilter_packet(demux, buf);
 		buf += 188;
 	}
 
-	spin_unlock_irqrestore(&demux->lock, flags);
+	spin_unlock(&demux->lock);
 }
 
 EXPORT_SYMBOL(dvb_dmx_swfilter_packets);
 
 void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count)
 {
-	unsigned long flags;
 	int p = 0, i, j;
 
-	spin_lock_irqsave(&demux->lock, flags);
+	spin_lock(&demux->lock);
 
 	if (demux->tsbufp) {
 		i = demux->tsbufp;
@@ -452,18 +449,17 @@ void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count)
 	}
 
 bailout:
-	spin_unlock_irqrestore(&demux->lock, flags);
+	spin_unlock(&demux->lock);
 }
 
 EXPORT_SYMBOL(dvb_dmx_swfilter);
 
 void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t count)
 {
-	unsigned long flags;
 	int p = 0, i, j;
 	u8 tmppack[188];
 
-	spin_lock_irqsave(&demux->lock, flags);
+	spin_lock(&demux->lock);
 
 	if (demux->tsbufp) {
 		i = demux->tsbufp;
@@ -504,7 +500,7 @@ void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t count)
 	}
 
 bailout:
-	spin_unlock_irqrestore(&demux->lock, flags);
+	spin_unlock(&demux->lock);
 }
 
 EXPORT_SYMBOL(dvb_dmx_swfilter_204);