[pulseaudio-discuss] PA 7.0 crash with KDE

[David Henningsson]

On 2015-10-16 10:35, Takashi Iwai wrote:
> On Fri, 16 Oct 2015 09:16:04 +0200,
> David Henningsson wrote:
>>
>> (Adding pulseaudio-discuss to CC)
>>
>> On 2015-10-15 16:26, Takashi Iwai wrote:
>>> Hi David,
>>>
>>> we got bug reports with PA 7.0 where the recent KDE crashes.
>>> It seems that srbchannel=no works around it, so there is still
>>> something fishy there.
>>>
>>> The bug report is found at
>>>     http://bugzilla.opensuse.org/show_bug.cgi?id=950487
>>
>> Hi Takashi and thanks for reporting.
>>
>> I've tried running PA 7.0's pactl under valgrind, and it reports no
>> errors here. Still, looking at the one of the backtraces the value of f
>> is something interesting:
>>
>> #6  flush (f=f at entry=0x4545454545454545) at pulsecore/fdsem.c:143
>> #7  0x00007fe30f378fc2 in pa_fdsem_before_poll (f=0x4545454545454545) at
>> pulsecore/fdsem.c:295
>> #8  0x00007fe30f38f697 in srbchannel_rwloop (sr=0x25bdd40) at
>> pulsecore/srbchannel.c:203
>>
>> Does 0x4545454545454545 mean anything specific on OpenSUSE? (Like, a
>> magic clear value or something?)
>
> I don't think it's openSUSE specific.  It's likely the guard put by
> either gcc or glibc.
> FWIW, we pass the default optimization flags like:
>    CFLAGS=-fmessage-length=0 -grecord-gcc-switches -O2 -Wall \
>      -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables \
>      -fasynchronous-unwind-tables -g -fPIE
>
> The problem was reported from both gcc-4.8 and gcc-5.x systems, so the
> gcc version is likely irrelevant.
>
>> Also, are there any distro patches to OpenSUSE and if so, where can I
>> find them?
>
> No, there is no patches apparently relevant with this.  Actually there are
> three patches, one is to check an additional environment check in
> start-pulseaudio-x11, another is to suppress an error log at
> sockaddr_prepare(), and the last is a fix in memset() size in
> echo-cancel/adrian-aec.c.  But all these should be safe.
>
> All sources, patches, build log and binaries are found in OBS, e.g. at
>    https://build.opensuse.org/package/show/multimedia:libs/pulseaudio

Ok, thanks.

I've been trying to analyze the backtrace.

My guess is that the srbchannel is being destroyed somehow, but I don't 
see how. Any chance we can get more info from this, e g, build 
pulseaudio's client library with -DDEBUG_SRBCHANNEL=1 and then get a log 
like this:

PULSE_LOG=99 pactl info

...which includes the crash?

Also, if the srbchannel gets destroyed and replaced by another 
srbchannel (eh?), it's possible that the below would help:

diff --git a/src/pulsecore/pstream.c b/src/pulsecore/pstream.c
index 8c14fbb..06063bb 100644
--- a/src/pulsecore/pstream.c
+++ b/src/pulsecore/pstream.c
@@ -223,7 +223,7 @@ static bool srb_callback(pa_srbchannel *srb, void 
*userdata) {
      pa_assert(p->srb == srb);

      do_pstream_read_write(p);
-    return p->srb != NULL;
+    return p->srb == srb;
  }


...but that's an even wilder guess, at this point.


-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic