[alsa-devel] [PATCH 21/31] ASoC: dapm: Use WARN_ON() instead of BUG_ON()

[Takashi Iwai]

At Thu, 7 Nov 2013 11:31:45 +0000,
Mark Brown wrote:
> 
> On Thu, Nov 07, 2013 at 08:31:59AM +0100, Takashi Iwai wrote:
> 
> > > But then we're still left with bombing out if the first half of the
> > > function ever changes.  The check is there for the benefit of the
> > > register handling, the fact that it's affecting events is just a side
> > > effect rather than the intention.
> 
> > Actually the check reg == w->reg must be always true for all pending
> > items, no matter at which point.  Otherwise BUG() would have hit.
> 
> Right, but that's not actually what the check is there for.  The loop is
> both doing an event check and building up the register value to write,
> the check is to tell us if we're confused about the register value since
> we'll end up writing to the wrong register during coalescing.
> 
> > That being said, maybe a cleaner way would be to run the check over
> > the loop once, and quit the function if anything inconsistent found.
> 
> Or do two passes, one for the registers and one for the events.  You
> could also reorder the loop to pull the events to the top and then do
> the check and skip between them and the value update, or simply remove
> the BUG().
> 
> Or just don't worry about it and leave the second loop alone since none
> of this is ideal - possibly the most helpful thing would be to insert a
> non-coalesced write for the out of place widget, though depending on why
> things are going wrong perhaps that'll just make things worse and we
> should be trying to unwind the entire transaction instead.  Unwinding
> the entire thing is going to be the generally safest but least helpful
> option.
> 
> My main concern here is not to confuse the code by having the check for
> the register value protecting an event call, that'll be confusing later
> on.  If you just want to fix the BUG()s do that alone, change them to
> WARN()s or whatever.

OK, back to square, I simplified the patch without extra error
handling, just replacing with WARN_ON() at that point.  The revised
patch is below.


Takashi

---
From: Takashi Iwai <tiwai at suse.de>
Subject: [PATCH] ASoC: dapm: Use WARN_ON() instead of BUG_ON()

Leaving BUG_ON() in a core layer like dapm is rather inappropriate as
it leads to panic(), even though sanity checks might be still useful
for debugging.
Instead, Use WARN_ON(), and handle the error cases accordingly.

Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/soc/soc-dapm.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index cc36caaf6443..36f4553a2973 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -1460,7 +1460,7 @@ static void dapm_seq_run_coalesced(struct snd_soc_card *card,
 			       power_list)->reg;
 
 	list_for_each_entry(w, pending, power_list) {
-		BUG_ON(reg != w->reg);
+		WARN_ON(reg != w->reg);
 		w->power = w->new_power;
 
 		mask |= w->mask << w->shift;
@@ -3359,8 +3359,9 @@ static int snd_soc_dai_link_event(struct snd_soc_dapm_widget *w,
 	u64 fmt;
 	int ret;
 
-	BUG_ON(!config);
-	BUG_ON(list_empty(&w->sources) || list_empty(&w->sinks));
+	if (WARN_ON(!config) ||
+	    WARN_ON(list_empty(&w->sources) || list_empty(&w->sinks)))
+		return -EINVAL;
 
 	/* We only support a single source and sink, pick the first */
 	source_p = list_first_entry(&w->sources, struct snd_soc_dapm_path,
@@ -3368,9 +3369,10 @@ static int snd_soc_dai_link_event(struct snd_soc_dapm_widget *w,
 	sink_p = list_first_entry(&w->sinks, struct snd_soc_dapm_path,
 				  list_source);
 
-	BUG_ON(!source_p || !sink_p);
-	BUG_ON(!sink_p->source || !source_p->sink);
-	BUG_ON(!source_p->source || !sink_p->sink);
+	if (WARN_ON(!source_p || !sink_p) ||
+	    WARN_ON(!sink_p->source || !source_p->sink) ||
+	    WARN_ON(!source_p->source || !sink_p->sink))
+		return -EINVAL;
 
 	source = source_p->source->priv;
 	sink = sink_p->sink->priv;
-- 
1.8.4.2