snd/pcm: fix snd_pcm_stream_lock*() irqs_disabled() splats

Locking functions previously using read_lock_irq()/read_lock_irqsave() were
changed to local_irq_disable/save(), leading to gripes.  Use nort variants.

|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:915
|in_atomic(): 0, irqs_disabled(): 1, pid: 5947, name: alsa-sink-ALC88
|CPU: 5 PID: 5947 Comm: alsa-sink-ALC88 Not tainted 3.18.7-rt1 #9
|Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.404 11/06/2014
| ffff880409316240 ffff88040866fa38 ffffffff815bdeb5 0000000000000002
| 0000000000000000 ffff88040866fa58 ffffffff81073c86 ffffffffa03b2640
| ffff88040239ec00 ffff88040866fa78 ffffffff815c3d34 ffffffffa03b2640
|Call Trace:
| [<ffffffff815bdeb5>] dump_stack+0x4f/0x9e
| [<ffffffff81073c86>] __might_sleep+0xe6/0x150
| [<ffffffff815c3d34>] __rt_spin_lock+0x24/0x50
| [<ffffffff815c4044>] rt_read_lock+0x34/0x40
| [<ffffffffa03a2979>] snd_pcm_stream_lock+0x29/0x70 [snd_pcm]
| [<ffffffffa03a355d>] snd_pcm_playback_poll+0x5d/0x120 [snd_pcm]
| [<ffffffff811937a2>] do_sys_poll+0x322/0x5b0
| [<ffffffff81193d48>] SyS_ppoll+0x1a8/0x1c0
| [<ffffffff815c4556>] system_call_fastpath+0x16/0x1b

Signed-off-by: Mike Galbraith <[email protected]>
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>

sound/core/pcm_native.c

@@ -135,7 +135,7 @@ EXPORT_SYMBOL_GPL(snd_pcm_stream_unlock);
 void snd_pcm_stream_lock_irq(struct snd_pcm_substream *substream)
 {
 	if (!substream->pcm->nonatomic)
-		local_irq_disable();
+		local_irq_disable_nort();
 	snd_pcm_stream_lock(substream);
 }
 EXPORT_SYMBOL_GPL(snd_pcm_stream_lock_irq);
@@ -150,15 +150,15 @@ void snd_pcm_stream_unlock_irq(struct snd_pcm_substream *substream)
 {
 	snd_pcm_stream_unlock(substream);
 	if (!substream->pcm->nonatomic)
-		local_irq_enable();
+		local_irq_enable_nort();
 }
 EXPORT_SYMBOL_GPL(snd_pcm_stream_unlock_irq);
 
 unsigned long _snd_pcm_stream_lock_irqsave(struct snd_pcm_substream *substream)
 {
 	unsigned long flags = 0;
 	if (!substream->pcm->nonatomic)
-		local_irq_save(flags);
+		local_irq_save_nort(flags);
 	snd_pcm_stream_lock(substream);
 	return flags;
 }
@@ -176,7 +176,7 @@ void snd_pcm_stream_unlock_irqrestore(struct snd_pcm_substream *substream,
 {
 	snd_pcm_stream_unlock(substream);
 	if (!substream->pcm->nonatomic)
-		local_irq_restore(flags);
+		local_irq_restore_nort(flags);
 }
 EXPORT_SYMBOL_GPL(snd_pcm_stream_unlock_irqrestore);