From 9535dce82c77679a230aa01cd58c699256e1da13 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Mon, 16 May 2016 20:54:46 -0400
Subject: [PATCH] Fix deadlocks in scrubbing, again, and better...

see eac6f98cbf97d9cdb240da978581ce21ec0d6f9c
---
 src/AudioIO.cpp | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/src/AudioIO.cpp b/src/AudioIO.cpp
index 4ece76a9a..e04f13db4 100644
--- a/src/AudioIO.cpp
+++ b/src/AudioIO.cpp
@@ -415,21 +415,12 @@ struct AudioIO::ScrubQueue
    void Nudge()
    {
       wxMutexLocker locker(mUpdating);
-      mAvailable.Signal();
-   }
-
-   void PoisonPill()
-   {
-      // Main thread is shutting down the scrubbing
-      wxMutexLocker locker(mUpdating);
-      mPoisoned = true;
+      mNudged = true;
       mAvailable.Signal();
    }
 
    bool Producer(double end, double maxSpeed, bool bySpeed, bool maySkip)
    {
-      wxASSERT(!mPoisoned);
-
       // Main thread indicates a scrubbing interval
 
       // MAY ADVANCE mLeadingIdx, BUT IT NEVER CATCHES UP TO mTrailingIdx.
@@ -471,9 +462,11 @@ struct AudioIO::ScrubQueue
       // MAY ADVANCE mMiddleIdx, WHICH MAY EQUAL mLeadingIdx, BUT DOES NOT PASS IT.
 
       wxMutexLocker locker(mUpdating);
-      while(!mPoisoned && mMiddleIdx == mLeadingIdx)
+      while(!mNudged && mMiddleIdx == mLeadingIdx)
          mAvailable.Wait();
 
+      mNudged = false;
+
       if (mMiddleIdx != mLeadingIdx)
       {
          // There is work in the queue
@@ -703,7 +696,7 @@ private:
    wxLongLong mLastScrubTimeMillis;
    mutable wxMutex mUpdating;
    mutable wxCondition mAvailable { mUpdating };
-   bool mPoisoned { false };
+   bool mNudged { false };
 };
 #endif
 
@@ -2199,7 +2192,7 @@ void AudioIO::StopStream()
 
    mAudioThreadFillBuffersLoopRunning = false;
    if (mScrubQueue)
-      mScrubQueue->PoisonPill();
+      mScrubQueue->Nudge();
 
    // Audacity can deadlock if it tries to update meters while
    // we're stopping PortAudio (because the meter updating code
@@ -2303,6 +2296,8 @@ void AudioIO::StopStream()
          // PRL:  Made it safe yield to avoid a certain recursive event processing in the
          // time ruler when switching from scrub to quick play.
          wxGetApp().SafeYield(nullptr, true); // Pass true for onlyIfNeeded to avoid recursive call error.
+         if (mScrubQueue)
+            mScrubQueue->Nudge();
          wxMilliSleep( 50 );
       }