PR libstdc++/50862
* include/std/condition_variable (condition_variable_any::wait): Fix
deadlock and ensure _Lock::lock() is called on exit.
(condition_variable_any::native_handle): Remove, as per LWG 1500.
* testsuite/30_threads/condition_variable_any/50862.cc: New.
Tested x86_64-linux, committed to trunk.
I plan to fix this on the 4.6 branch too, it's a shame it's too late for 4.6.2
Index: include/std/condition_variable
===================================================================
--- include/std/condition_variable (revision 180411)
+++ include/std/condition_variable (working copy)
@@ -203,10 +203,19 @@
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() { _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);
}
@@ -254,10 +263,6 @@
wait_for(_Lock& __lock,
const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
{ return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p));
}
-
- native_handle_type
- native_handle()
- { return _M_cond.native_handle(); }
};
// @} group condition_variables
Index: testsuite/30_threads/condition_variable_any/50862.cc
===================================================================
--- testsuite/30_threads/condition_variable_any/50862.cc (revision 0)
+++ testsuite/30_threads/condition_variable_any/50862.cc (revision 0)
@@ -0,0 +1,75 @@
+// { 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 "" }
+
+// 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(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(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();
+ }
+
+}
