From eac6f98cbf97d9cdb240da978581ce21ec0d6f9c Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Mon, 16 May 2016 17:54:54 -0400
Subject: [PATCH] Avoid deadlocks that sometimes happened when starting a
 scrub...

... as a consequence of commit 52910f4f07d41904e5f8cc5fdc5e7f8484468a00
---
 src/AudioIO.cpp | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/AudioIO.cpp b/src/AudioIO.cpp
index 6ba2dc7fa..4ece76a9a 100644
--- a/src/AudioIO.cpp
+++ b/src/AudioIO.cpp
@@ -410,6 +410,14 @@ struct AudioIO::ScrubQueue
       return previous.mS1 / mRate;
    }
 
+   // This is for avoiding deadlocks while starting a scrub:
+   // Audio stream needs to be unblocked
+   void Nudge()
+   {
+      wxMutexLocker locker(mUpdating);
+      mAvailable.Signal();
+   }
+
    void PoisonPill()
    {
       // Main thread is shutting down the scrubbing
@@ -478,8 +486,7 @@ struct AudioIO::ScrubQueue
       }
       else
       {
-         wxASSERT(mPoisoned);
-         // We got the shut-down signal
+         // We got the shut-down signal, or we got nudged
          startSample = endSample = duration = -1L;
       }
    }
@@ -1874,8 +1881,11 @@ int AudioIO::StartStream(const WaveTrackArray &playbackTracks,
    // FillBuffers will ALWAYS get called from the Audio thread.
    mAudioThreadShouldCallFillBuffersOnce = true;
 
-   while( mAudioThreadShouldCallFillBuffersOnce == true )
+   while( mAudioThreadShouldCallFillBuffersOnce == true ) {
+      if (mScrubQueue)
+         mScrubQueue->Nudge();
       wxMilliSleep( 50 );
+   }
 
 #ifdef EXPERIMENTAL_MIDI_OUT
    // if no playback, reset the midi time to zero to roughly sync