[igt-dev] [PATCH i-g-t v3 6/6] lib/igt_kmod: properly handle pipewire-pulse

[Mauro Carvalho Chehab]

On Mon, 16 May 2022 15:35:14 +0200
Mauro Carvalho Chehab <mauro.chehab at linux.intel.com> wrote:

> On Mon, 16 May 2022 14:49:21 +0200
> Andi Shyti <andi.shyti at linux.intel.com> wrote:
> 
> > Hi Mauro,
> >   
> > > +static void pipewire_reserve_wait(int pipewire_pulse_pid)
> > > +{
> > > +	char xdg_dir[PATH_MAX];
> > > +	const char *homedir;
> > > +	struct passwd *pw;
> > > +	proc_t *proc_info;
> > > +	PROCTAB *proc;
> > > +
> > > +	igt_fork(child, 1) {
> > > +		igt_info("Preventing pipewire-pulse to use the audio drivers\n");
> > > +
> > > +		proc = openproc(PROC_FILLCOM | PROC_FILLSTAT | PROC_FILLARG);
> > > +		igt_assert(proc != NULL);
> > > +
> > > +		while ((proc_info = readproc(proc, NULL))) {
> > > +			if (pipewire_pulse_pid == proc_info->tid)
> > > +				break;
> > > +			freeproc(proc_info);
> > > +		}
> > > +		closeproc(proc);
> > > +
> > > +		/* Sanity check: if it can't find the process, it means it has gone */
> > > +		if (pipewire_pulse_pid != proc_info->tid)
> > > +			exit(0);
> > > +
> > > +		pw = getpwuid(proc_info->euid);
> > > +		homedir = pw->pw_dir;
> > > +		snprintf(xdg_dir, sizeof(xdg_dir), "/run/user/%d", proc_info->euid);
> > > +		setgid(proc_info->egid);
> > > +		setuid(proc_info->euid);
> > > +		clearenv();
> > > +		setenv("HOME", homedir, 1);
> > > +		setenv("XDG_RUNTIME_DIR",xdg_dir, 1);
> > > +		freeproc(proc_info);
> > > +
> > > +		exit(system("pw-reserve -n Audio0 -r"));    
> > 
> > no exit...
> >   
> > > +	}    
> > 
> > ... and waitchild().
> > 
> > Like in patch 1 :)  
> 
> OK!

Actually, no!

See, this is what happens if it calls waitchild():

	IGT-Version: 1.26-g30915d22 (x86_64) (Linux: 5.18.0-rc7-drm-ad75b5b819c9+ x86_64)
	Starting subtest: unbind-rebind
	process 12096 (alsactl) is using audio device. Should be terminated.
	process 12801 (pipewire-pulse) is using audio device. Should be requested to stop using them.
	Preventing pipewire-pulse to use the audio drivers
	Device Audio0 can not be acquired: Success
	reserve acquired
	<wait forever, as pw-reserve will run forever>

By using exit(system()) there, everything works like a charm:

	IGT-Version: 1.26-gac8dabf6 (x86_64) (Linux: 5.18.0-rc7-drm-ad75b5b819c9+ x86_64)
	Starting subtest: unbind-rebind
	process 12801 (pipewire-pulse) is using audio device. Should be requested to stop using them.
	Preventing pipewire-pulse to use the audio drivers
	Device Audio0 can not be acquired: Success
	reserve acquired
	Unloaded audio driver snd_hda_intel
	Realoading snd_hda_intel
	Subtest unbind-rebind: SUCCESS (2.755s)


See, what we want is to run pw-reserve in backgroud, then remove
snd_hda_intel and finally kill it with SIGTERM.

Regards,
Mauro