[Libreoffice-commits] core.git: comphelper/source

[Stephan Bergmann]

 comphelper/source/misc/threadpool.cxx |   18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

New commits:
commit d36b3bcb7e08f7f73709b7afe9b8f9ec22a0fcd2
Author: Stephan Bergmann <sbergman at redhat.com>
Date:   Thu Dec 1 12:35:36 2016 +0100

    Fix race in ThreadTaskTag
    
    Assume T0 calls ThreadPool::pushTask twice, then ThreadPool::waitUntilDone:
    
    T0 calls ThreadTaskTag::onTaskPushed:
      mnTasksWorking = 1, maTasksComplete.reset
    
    T1 runs the 1st task to completion and calls ThreadTaskTag::onTaskWorkerDone:
      mnTasksWorking = 0; suspended...
    
    T0 calls ThreadTaskTag::onTaskPushed:
      mnTaskWorking = 1, maTasksComplete.reset
    
    T1 continues in the call to ThreadTaskTag::onTaskWorkerDone:
      ..., maTasksComplete.set
    
    T0 calls ThreadTaskTag::waitUntilDone and immediately returns
    
    T2 only now starts to run the 2nd task
    
    Change-Id: Ic29101a4791fca2a1a4d54b559f10ff706e8a20d

diff --git a/comphelper/source/misc/threadpool.cxx b/comphelper/source/misc/threadpool.cxx
index 346c171..0fda264 100644
--- a/comphelper/source/misc/threadpool.cxx
+++ b/comphelper/source/misc/threadpool.cxx
@@ -26,8 +26,9 @@ static thread_local bool gbIsWorkerThread;
 // used to group thread-tasks for waiting in waitTillDone()
 class COMPHELPER_DLLPUBLIC ThreadTaskTag
 {
-    oslInterlockedCount  mnTasksWorking;
-    osl::Condition       maTasksComplete;
+    osl::Mutex mMutex;
+    std::size_t mnTasksWorking;
+    osl::Condition maTasksComplete;
 
 public:
     ThreadTaskTag();
@@ -302,17 +303,18 @@ ThreadTaskTag::ThreadTaskTag() : mnTasksWorking(0)
 
 void ThreadTaskTag::onTaskPushed()
 {
-    oslInterlockedCount n = osl_atomic_increment(&mnTasksWorking);
-    assert( n < 65536 ); // sanity checking
-    (void)n; // avoid -Wunused-variable in release build
+    osl::MutexGuard g(mMutex);
+    assert( mnTasksWorking < 65535 ); // sanity checking
+    ++mnTasksWorking;
     maTasksComplete.reset();
 }
 
 void ThreadTaskTag::onTaskWorkerDone()
 {
-    sal_Int32 nCount = osl_atomic_decrement(&mnTasksWorking);
-    assert(nCount >= 0);
-    if (nCount == 0)
+    osl::MutexGuard g(mMutex);
+    assert(mnTasksWorking > 0);
+    --mnTasksWorking;
+    if (mnTasksWorking == 0)
         maTasksComplete.set();
 }