From: Jonathan Wakely <jwakely.gcc@gmail.com>
Date: Mon, 19 Dec 2011 00:34:29 +0000 (+0000)
Subject: re PR libstdc++/50862 (deadlock in std::condition_variable_any)
X-Git-Tag: releases/gcc-4.6.3~246
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d10d3240d7d6998b22bd7b62cd48eabacef85773;p=thirdparty%2Fgcc.git

re PR libstdc++/50862 (deadlock in std::condition_variable_any)

	PR libstdc++/50862
	* include/std/condition_variable (condition_variable_any::wait): Fix
	deadlock and ensure _Lock::lock() is called on exit.
	* testsuite/30_threads/condition_variable_any/50862.cc: New.

From-SVN: r182467
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 62a2d4c18e95..5978d7b7a066 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2011-12-19  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
+	PR libstdc++/50862
+	* include/std/condition_variable (condition_variable_any::wait): Fix
+	deadlock and ensure _Lock::lock() is called on exit.
+	* testsuite/30_threads/condition_variable_any/50862.cc: New.
+
 2011-12-18  Jonathan Wakely  <jwakely.gcc@gmail.com>
 
 	PR libstdc++/51540
diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index a0a3c08794a1..ff65dc49ce44 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -198,10 +198,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       void
       wait(_Lock& __lock)
       {
-        unique_lock<mutex> __my_lock(_M_mutex);
-        __lock.unlock();
-        _M_cond.wait(__my_lock);
-        __lock.lock();
+	// scoped unlock - unlocks in ctor, re-locks in dtor
+	struct _Unlock {
+	  explicit _Unlock(_Lock& __lk) : _M_lock(__lk) { __lk.unlock(); }
+	  ~_Unlock() noexcept(false)
+	  {
+	    if (uncaught_exception())
+	      __try { _M_lock.lock(); } __catch(...) { }
+	    else
+	      _M_lock.lock();
+	  }
+	  _Lock& _M_lock;
+	};
+
+	unique_lock<mutex> __my_lock(_M_mutex);
+	_Unlock __unlock(__lock);
+	// _M_mutex must be unlocked before re-locking __lock so move
+	// ownership of _M_mutex lock to an object with shorter lifetime.
+	unique_lock<mutex> __my_lock2(std::move(__my_lock));
+	_M_cond.wait(__my_lock2);
       }
       
 
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable_any/50862.cc b/libstdc++-v3/testsuite/30_threads/condition_variable_any/50862.cc
new file mode 100644
index 000000000000..b85a5e136266
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable_any/50862.cc
@@ -0,0 +1,80 @@
+// { dg-do run { target *-*-freebsd* *-*-netbsd* *-*-linux* *-*-solaris* *-*-cygwin *-*-darwin* alpha*-*-osf* mips-sgi-irix6* } }
+// { dg-options " -std=gnu++0x -pthread" { target *-*-freebsd* *-*-netbsd* *-*-linux* alpha*-*-osf* mips-sgi-irix6* } }
+// { dg-options " -std=gnu++0x -pthreads" { target *-*-solaris* } }
+// { dg-options " -std=gnu++0x " { target *-*-cygwin *-*-darwin* } }
+// { dg-require-cstdint "" }
+// { dg-require-gthreads "" }
+// { dg-require-sched-yield "" }
+ 
+// Copyright (C) 2011 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>. 
+
+#include <condition_variable>
+#include <thread>
+#include <mutex>
+#include <array>
+#include <sstream>
+
+struct scoped_thread
+{
+  ~scoped_thread() { if (t.joinable()) t.join(); }
+  std::thread t;
+};
+
+int main()
+{
+  typedef std::unique_lock<std::mutex> Lock;
+
+  std::mutex                  m;
+  std::condition_variable_any cond;
+  unsigned int                product = 0;
+  const unsigned int          count = 10;
+
+  // writing to stream causes timing changes which makes deadlock easier
+  // to reproduce - do not remove
+  std::ostringstream out;
+
+  // create consumers
+  std::array<scoped_thread, 2> threads;
+  for (std::size_t i = 0; i < threads.size(); ++i)
+    threads[i].t
+      = std::thread( [&]
+		     {
+		       for (unsigned int i = 0; i < count; ++i)
+			 {
+			   std::this_thread::yield();
+			   Lock lock(m);
+			   while(product == 0)
+			     cond.wait(lock);
+			   out << "got product "
+			       << std::this_thread::get_id()
+			       << ' ' << product << std::endl;
+			   --product;
+			 }
+		     } );
+
+  // single producer
+  for (std::size_t i = 0; i < threads.size() * count; ++i)
+    {
+      std::this_thread::yield();
+      Lock lock(m);
+      ++product;
+      out << "setting product " << std::this_thread::get_id()
+	  << ' ' << product << std::endl;
+      cond.notify_one();
+    }
+}