From 9d811bf080bc12cc3b510d264619bbeefe29790f Mon Sep 17 00:00:00 2001
From: Tobias Doerffel <tobias.doerffel@gmail.com>
Date: Fri, 14 Aug 2009 12:13:33 +0200
Subject: [PATCH] MidiAlsaSeq: improved MIDI event polling loop

Use poll() with a finite timeout so we can quit the thread properly
without manually writing stuff into the pipe.

Check for pending events at the beginning of the loop so we can't end up
in an endless loop.

Furthermore check return value of snd_seq_event_input() and get out of
loop if it indicates an error.
---
 src/core/midi/MidiAlsaSeq.cpp | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/core/midi/MidiAlsaSeq.cpp b/src/core/midi/MidiAlsaSeq.cpp
index b7b7c6f55..158aef569 100644
--- a/src/core/midi/MidiAlsaSeq.cpp
+++ b/src/core/midi/MidiAlsaSeq.cpp
@@ -36,6 +36,8 @@
 
 #ifdef LMMS_HAVE_ALSA
 
+const int EventPollTimeOut = 250;
+
 
 MidiAlsaSeq::MidiAlsaSeq() :
 	MidiClient(),
@@ -95,10 +97,7 @@ MidiAlsaSeq::~MidiAlsaSeq()
 	if( isRunning() )
 	{
 		m_quit = true;
-		// wake up input queue
-		if( write( m_pipe[1], "\n", 1 ) )
-			/* fix warning */;
-		wait( 1000 );
+		wait( EventPollTimeOut*2 );
 
 		snd_seq_stop_queue( m_seqHandle, m_queueID, NULL );
 		snd_seq_free_queue( m_seqHandle, m_queueID );
@@ -405,26 +404,36 @@ void MidiAlsaSeq::run()
 
 	while( m_quit == false )
 	{
-		if( poll( pollfd_set, pollfd_count, -1 ) == -1 )
+		int pollRet = poll( pollfd_set, pollfd_count, EventPollTimeOut );
+		if( pollRet == 0 )
+		{
+			continue;
+		}
+		else if( pollRet == -1 )
 		{
 			// gdb may interrupt the poll
 			if( errno == EINTR )
 			{
 				continue;
 			}
-			perror( __FILE__ ": poll" );
+			qCritical( "error while polling ALSA sequencer handle" );
+			break;
 		}
 		// shutdown?
-		if( pollfd_set[0].revents )
+		if( m_quit )
 		{
 			break;
 		}
 
-		do	// while event queue is not empty
+		// while event queue is not empty
+		while( snd_seq_event_input_pending( m_seqHandle, true ) > 0 )
 		{
 
 		snd_seq_event_t * ev;
-		snd_seq_event_input( m_seqHandle, &ev );
+		if( snd_seq_event_input( m_seqHandle, &ev ) < 0 )
+		{
+			break;
+		}
 
 		MidiPort * dest = NULL;
 		for( int i = 0; i < m_portIDs.size(); ++i )
@@ -515,9 +524,9 @@ void MidiAlsaSeq::run()
 					"ALSA-sequencer: unhandled input "
 						"event %d\n", ev->type );
 				break;
-		}
+		}	// end switch
 
-		} while( snd_seq_event_input_pending( m_seqHandle, 0 ) > 0 );
+		}	// end while
 
 	}