V4L/DVB (10572): Revert commit dda06a8e4610757def753ee3a541a0b1a1feb36b

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>

1 files changed, 6 insertions, 10 deletions

diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c
index a2c1fd5..e2eca0b 100644
--- a/drivers/media/dvb/dvb-core/dvb_demux.c
+++ b/drivers/media/dvb/dvb-core/dvb_demux.c
@@ -399,9 +399,7 @@ 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)
@@ -409,17 +407,16 @@ void dvb_dmx_swfilter_packets(struct dvb_demux *demux, const u8 *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);