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gcc/gcc41-rh426846.patch

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2007-10-10 Jason Merrill <jason@redhat.com>
* libsupc++/guard.cc (struct mutex_wrapper): Move into
anonymous namespace.
2007-10-09 Zhou Drangon <drangon.mail@gmail.com>
PR libstdc++/33682
* libsupc++/guard.cc: Make single conditional variable
implementation dependent to __GTHREAD_HAS_COND.
2007-10-05 Hans-Peter Nilsson <hp@axis.com>
* gthr-single.h: Revert last change.
2007-10-04 Doug Kwan <dougkwan@google.com>
* gthr-posix.h (__gthread_cond_broadcast, __gthread_cond_wait,
__gthread_cond_wait_recursive): Add to extend interface for POSIX
conditional variables. (__GTHREAD_HAS_COND): Macro defined to signify
support of conditional variables.
* gthr-posix95.h (__gthread_cond_broadcast, __gthread_cond_wait,
__gthread_cond_wait_recursive): Add to extend interface for POSIX
conditional variables. (__GTHREAD_HAS_COND): Macro defined to signify
support of conditional variables.
* gthr-single.h (__gthread_cond_broadcast, __gthread_cond_wait,
__gthread_cond_wait_recursive): Add to extend interface for POSIX
conditional variables.
* gthr.h: Update comments to document new interface.
* include/ext/concurrent.h (class __mutex,
class __recursive_mutex): Add new method gthread_mutex to access
inner gthread mutex.
[__GTHREAD_HAS_COND] (class __concurrence_broadcast_error,
class __concurrence_wait_error, class __cond): Add.
* libsupc++/guard.cc (recursive_push, recursive_pop): Delete.
(init_in_progress_flag, set_init_in_progress_flag): Add to
replace recursive_push and recursive_pop.
(throw_recursive_init_exception): Add.
(acquire, __cxa_guard_acquire, __cxa_guard_abort and
__cxa_guard_release): [__GTHREAD_HAS_COND] Use a conditional
for synchronization of static variable initialization.
The global mutex is only held briefly when guards are
accessed. [!__GTHREAD_HAS_COND] Fall back to the old code,
which deadlocks.
* testsuite/thread/guard.cc: Add new test. It deadlocks with the
old locking code in libstdc++-v3/libsup++/guard.cc.
--- gcc/gthr.h (revision 129029)
+++ gcc/gthr.h (revision 129030)
@@ -81,6 +81,24 @@ Software Foundation, 51 Franklin Street,
int __gthread_recursive_mutex_trylock (__gthread_recursive_mutex_t *mutex);
int __gthread_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex);
+ The following are supported in POSIX threads only. They are required to
+ fix a deadlock in static initialization inside libsupc++. The header file
+ gthr-posix.h defines a symbol __GTHREAD_HAS_COND to signify that these extra
+ features are supported.
+
+ Types:
+ __gthread_cond_t
+
+ Macros:
+ __GTHREAD_COND_INIT
+ __GTHREAD_COND_INIT_FUNCTION
+
+ Interface:
+ int __gthread_cond_broadcast (__gthread_cond_t *cond);
+ int __gthread_cond_wait (__gthread_cond_t *cond, __gthread_mutex_t *mutex);
+ int __gthread_cond_wait_recursive (__gthread_cond_t *cond,
+ __gthread_recursive_mutex_t *mutex);
+
All functions returning int should return zero on success or the error
number. If the operation is not supported, -1 is returned.
--- gcc/gthr-posix.h (revision 129029)
+++ gcc/gthr-posix.h (revision 129030)
@@ -47,6 +47,11 @@ typedef pthread_key_t __gthread_key_t;
typedef pthread_once_t __gthread_once_t;
typedef pthread_mutex_t __gthread_mutex_t;
typedef pthread_mutex_t __gthread_recursive_mutex_t;
+typedef pthread_cond_t __gthread_cond_t;
+
+/* POSIX like conditional variables are supported. Please look at comments
+ in gthr.h for details. */
+#define __GTHREAD_HAS_COND 1
#define __GTHREAD_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
#define __GTHREAD_ONCE_INIT PTHREAD_ONCE_INIT
@@ -57,6 +62,7 @@ typedef pthread_mutex_t __gthread_recurs
#else
#define __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION __gthread_recursive_mutex_init_function
#endif
+#define __GTHREAD_COND_INIT PTHREAD_COND_INITIALIZER
#if SUPPORTS_WEAK && GTHREAD_USE_WEAK
# ifndef __gthrw_pragma
@@ -88,6 +94,8 @@ __gthrw3(pthread_mutex_lock)
__gthrw3(pthread_mutex_trylock)
__gthrw3(pthread_mutex_unlock)
__gthrw3(pthread_mutex_init)
+__gthrw3(pthread_cond_broadcast)
+__gthrw3(pthread_cond_wait)
#else
__gthrw(pthread_once)
__gthrw(pthread_getspecific)
@@ -98,6 +106,8 @@ __gthrw(pthread_mutex_lock)
__gthrw(pthread_mutex_trylock)
__gthrw(pthread_mutex_unlock)
__gthrw(pthread_mutex_init)
+__gthrw(pthread_cond_broadcast)
+__gthrw(pthread_cond_wait)
#endif
__gthrw(pthread_key_create)
@@ -110,20 +120,16 @@ __gthrw(pthread_mutexattr_destroy)
#if defined(_LIBOBJC) || defined(_LIBOBJC_WEAK)
/* Objective-C. */
#if defined(__osf__) && defined(_PTHREAD_USE_MANGLED_NAMES_)
-__gthrw3(pthread_cond_broadcast)
__gthrw3(pthread_cond_destroy)
__gthrw3(pthread_cond_init)
__gthrw3(pthread_cond_signal)
-__gthrw3(pthread_cond_wait)
__gthrw3(pthread_exit)
__gthrw3(pthread_mutex_destroy)
__gthrw3(pthread_self)
#else
-__gthrw(pthread_cond_broadcast)
__gthrw(pthread_cond_destroy)
__gthrw(pthread_cond_init)
__gthrw(pthread_cond_signal)
-__gthrw(pthread_cond_wait)
__gthrw(pthread_exit)
__gthrw(pthread_mutex_destroy)
__gthrw(pthread_self)
@@ -737,6 +743,25 @@ __gthread_recursive_mutex_unlock (__gthr
return __gthread_mutex_unlock (mutex);
}
+static inline int
+__gthread_cond_broadcast (__gthread_cond_t *cond)
+{
+ return __gthrw_(pthread_cond_broadcast) (cond);
+}
+
+static inline int
+__gthread_cond_wait (__gthread_cond_t *cond, __gthread_mutex_t *mutex)
+{
+ return __gthrw_(pthread_cond_wait) (cond, mutex);
+}
+
+static inline int
+__gthread_cond_wait_recursive (__gthread_cond_t *cond,
+ __gthread_recursive_mutex_t *mutex)
+{
+ return __gthread_cond_wait (cond, mutex);
+}
+
#endif /* _LIBOBJC */
#endif /* ! GCC_GTHR_POSIX_H */
--- gcc/gthr-posix95.h (revision 129029)
+++ gcc/gthr-posix95.h (revision 129030)
@@ -45,6 +45,11 @@ Software Foundation, 51 Franklin Street,
typedef pthread_key_t __gthread_key_t;
typedef pthread_once_t __gthread_once_t;
typedef pthread_mutex_t __gthread_mutex_t;
+typedef pthread_cond_t __gthread_cond_t;
+
+/* POSIX like conditional variables are supported. Please look at comments
+ in gthr.h for details. */
+#define __GTHREAD_HAS_COND 1
typedef struct {
long depth;
@@ -55,6 +60,7 @@ typedef struct {
#define __GTHREAD_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
#define __GTHREAD_ONCE_INIT PTHREAD_ONCE_INIT
#define __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION __gthread_recursive_mutex_init_function
+#define __GTHREAD_COND_INIT PTHREAD_COND_INITIALIZER
#if SUPPORTS_WEAK && GTHREAD_USE_WEAK
# define __gthrw(name) \
@@ -81,14 +87,14 @@ __gthrw(pthread_mutexattr_init)
__gthrw(pthread_mutexattr_destroy)
__gthrw(pthread_mutex_init)
+__gthrw(pthread_cond_broadcast)
+__gthrw(pthread_cond_wait)
#if defined(_LIBOBJC) || defined(_LIBOBJC_WEAK)
/* Objective-C. */
-__gthrw(pthread_cond_broadcast)
__gthrw(pthread_cond_destroy)
__gthrw(pthread_cond_init)
__gthrw(pthread_cond_signal)
-__gthrw(pthread_cond_wait)
__gthrw(pthread_exit)
__gthrw(pthread_mutex_destroy)
#ifdef _POSIX_PRIORITY_SCHEDULING
@@ -719,6 +725,25 @@ __gthread_recursive_mutex_unlock (__gthr
return 0;
}
+static inline int
+__gthread_cond_broadcast (__gthread_cond_t *cond)
+{
+ return __gthrw_(pthread_cond_broadcast) (cond);
+}
+
+static inline int
+__gthread_cond_wait (__gthread_cond_t *cond, __gthread_mutex_t *mutex)
+{
+ return __gthrw_(pthread_cond_wait) (cond, mutex);
+}
+
+static inline int
+__gthread_cond_wait_recursive (__gthread_cond_t *cond,
+ __gthread_recursive_mutex_t *mutex)
+{
+ return __gthrw_(pthread_cond_wait) (cond, mutex->actual);
+}
+
#endif /* _LIBOBJC */
#endif /* ! GCC_GTHR_POSIX_H */
--- libstdc++-v3/libsupc++/guard.cc (revision 129029)
+++ libstdc++-v3/libsupc++/guard.cc (revision 129218)
@@ -34,6 +34,9 @@
#include <bits/c++config.h>
#include <bits/gthr.h>
#include <bits/atomicity.h>
+#if defined(__GTHREAD_HAS_COND) && !defined(__GTHREAD_COND_INIT)
+#undef __GTHREAD_HAS_COND
+#endif
// The IA64/generic ABI uses the first byte of the guard variable.
// The ARM EABI uses the least significant bit.
@@ -46,7 +49,7 @@ namespace
// This is a static class--the need for a static initialization function
// to pass to __gthread_once precludes creating multiple instances, though
// I suppose you could achieve the same effect with a template.
- class static_mutex
+ struct static_mutex
{
static __gthread_recursive_mutex_t mutex;
@@ -85,8 +88,30 @@ namespace
{
__gthread_recursive_mutex_unlock (&mutex);
}
+
+ // Simple wrapper for exception safety.
+ struct mutex_wrapper
+ {
+ bool unlock;
+ mutex_wrapper() : unlock(true)
+ { static_mutex::lock(); }
+
+ ~mutex_wrapper()
+ {
+ if (unlock)
+ static_mutex::unlock();
+ }
+ };
}
+#ifdef __GTHREAD_HAS_COND
+namespace
+{
+ // A single conditional variable controlling all static initializations.
+ static __gthread_cond_t static_cond = __GTHREAD_COND_INIT;
+}
+#endif
+
#ifndef _GLIBCXX_GUARD_TEST_AND_ACQUIRE
inline bool
__test_and_acquire (__cxxabiv1::__guard *g)
@@ -135,19 +160,43 @@ namespace __gnu_cxx
recursive_init::~recursive_init() throw() { }
}
+//
+// Here are C++ run-time routines for guarded initiailization of static
+// variables. There are 4 scenarios under which these routines are called:
+//
+// 1. Threads not supported (__GTHREADS not defined)
+// 2. Threads are supported but not enabled at run-time.
+// 3. Threads enabled at run-time but __gthreads_* are not fully POSIX.
+// 4. Threads enabled at run-time and __gthreads_* support all POSIX threads
+// primitives we need here.
+//
+// The old code supported scenarios 1-3 but was broken since it used a global
+// mutex for all threads and had the mutex locked during the whole duration of
+// initlization of a guarded static variable. The following created a dead-lock
+// with the old code.
+//
+// Thread 1 acquires the global mutex.
+// Thread 1 starts initializing static variable.
+// Thread 1 creates thread 2 during initialization.
+// Thread 2 attempts to acuqire mutex to initialize another variable.
+// Thread 2 blocks since thread 1 is locking the mutex.
+// Thread 1 waits for result from thread 2 and also blocks. A deadlock.
+//
+// The new code here can handle this situation and thus is more robust. Howere,
+// we need to use the POSIX thread conditional variable, which is not supported
+// in all platforms, notably older versions of Microsoft Windows. The gthr*.h
+// headers define a symbol __GTHREAD_HAS_COND for platforms that support POSIX
+// like conditional variables. For platforms that do not support conditional
+// variables, we need to fall back to the old code.
namespace __cxxabiv1
{
static inline int
- recursion_push (__guard* g)
- {
- return ((char *)g)[1]++;
- }
+ init_in_progress_flag(__guard* g)
+ { return ((char *)g)[1]; }
static inline void
- recursion_pop (__guard* g)
- {
- --((char *)g)[1];
- }
+ set_init_in_progress_flag(__guard* g, int v)
+ { ((char *)g)[1] = v; }
static int
acquire_1 (__guard *g)
@@ -155,7 +204,7 @@ namespace __cxxabiv1
if (_GLIBCXX_GUARD_TEST (g))
return 0;
- if (recursion_push (g))
+ if (init_in_progress_flag (g))
{
#ifdef __EXCEPTIONS
throw __gnu_cxx::recursive_init();
@@ -164,6 +213,7 @@ namespace __cxxabiv1
__builtin_trap ();
#endif
}
+ set_init_in_progress_flag(g, 1);
return 1;
}
@@ -179,28 +229,40 @@ namespace __cxxabiv1
if (__gthread_active_p ())
{
- // Simple wrapper for exception safety.
- struct mutex_wrapper
- {
- bool unlock;
- mutex_wrapper (): unlock(true)
- {
- static_mutex::lock ();
- }
- ~mutex_wrapper ()
- {
- if (unlock)
- static_mutex::unlock ();
- }
- } mw;
+ mutex_wrapper mw;
- if (acquire_1 (g))
- {
- mw.unlock = false;
- return 1;
+ while (1) // When this loop is executing, mutex is locked.
+ {
+#ifdef __GTHREAD_HAS_COND
+ // The static is allready initialized.
+ if (_GLIBCXX_GUARD_TEST(g))
+ return 0; // The mutex will be unlocked via wrapper
+
+ if (init_in_progress_flag(g))
+ {
+ // The guarded static is currently being initialized by
+ // another thread, so we release mutex and wait for the
+ // conditional variable. We will lock the mutex again after
+ // this.
+ __gthread_cond_wait_recursive(&static_cond,
+ &static_mutex::mutex);
+ }
+ else
+ {
+ set_init_in_progress_flag(g, 1);
+ return 1; // The mutex will be unlocked via wrapper.
+ }
+#else
+ // This provides compatibility with older systems not supporting
+ // POSIX like conditional variables.
+ if (acquire_1 (g))
+ {
+ mw.unlock = false;
+ return 1; // The mutex still locked.
+ }
+ return 0; // The mutex will be unlocked via wrapper.
+#endif
}
-
- return 0;
}
#endif
@@ -210,8 +272,24 @@ namespace __cxxabiv1
extern "C"
void __cxa_guard_abort (__guard *g)
{
- recursion_pop (g);
-#ifdef __GTHREADS
+#ifdef __GTHREAD_HAS_COND
+ if (__gthread_active_p())
+ {
+ mutex_wrapper mw;
+
+ set_init_in_progress_flag(g, 0);
+
+ // If we abort, we still need to wake up all other threads waiting for
+ // the conditional variable.
+ __gthread_cond_broadcast(&static_cond);
+ return;
+ }
+#endif
+
+ set_init_in_progress_flag(g, 0);
+#if defined(__GTHREADS) && !defined(__GTHREAD_HAS_COND)
+ // This provides compatibility with older systems not supporting POSIX like
+ // conditional variables.
if (__gthread_active_p ())
static_mutex::unlock ();
#endif
@@ -220,11 +298,27 @@ namespace __cxxabiv1
extern "C"
void __cxa_guard_release (__guard *g)
{
- recursion_pop (g);
+#ifdef __GTHREAD_HAS_COND
+ if (__gthread_active_p())
+ {
+ mutex_wrapper mw;
+
+ set_init_in_progress_flag(g, 0);
+ _GLIBCXX_GUARD_SET_AND_RELEASE(g);
+
+ __gthread_cond_broadcast(&static_cond);
+ return;
+ }
+#endif
+
+ set_init_in_progress_flag(g, 0);
_GLIBCXX_GUARD_SET_AND_RELEASE (g);
-#ifdef __GTHREADS
- if (__gthread_active_p ())
- static_mutex::unlock ();
+
+#if defined(__GTHREADS) && !defined(__GTHREAD_HAS_COND)
+ // This provides compatibility with older systems not supporting POSIX like
+ // conditional variables.
+ if (__gthread_active_p())
+ static_mutex::unlock();
#endif
}
}
--- libstdc++-v3/testsuite/thread/guard.cc (revision 0)
+++ libstdc++-v3/testsuite/thread/guard.cc (revision 129030)
@@ -0,0 +1,67 @@
+//
+// Copyright (C) 2007 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 2, 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 COPYING. If not, write to the Free
+// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+// USA.
+
+// { dg-do run { target *-*-freebsd* *-*-netbsd* *-*-linux* *-*-solaris* *-*-cygwin *-*-darwin* alpha*-*-osf* } }
+// { dg-options "-pthread" { target *-*-freebsd* *-*-netbsd* *-*-linux* *-*-solaris* *-*-darwin* alpha*-*-osf* } }
+
+#include <cstdlib>
+#include <pthread.h>
+
+// This used to deadlock with the old libstdc++ because there is only one
+// global mutex guarding initialization of statics and it is held during by
+// the initializer thread of a static until the variable is completely
+// initialized. If the initializer thread creates and waits for another thread
+// which also initializes a static variable, there will be a deadlock because
+// the first thread is holding the mutex and waiting for the second thread,
+// which is blocked when it is acquiring the mutex.
+
+int
+get_bar (void)
+{
+ return 1;
+}
+
+void*
+do_something (void *arg)
+{
+ static int bar = get_bar ();
+ return NULL;
+}
+
+int
+get_foo (void)
+{
+ int status;
+ pthread_t new_thread;
+
+ if (pthread_create (&new_thread, NULL, do_something, NULL) != 0)
+ std::abort ();
+
+ if (pthread_join (new_thread, NULL) != 0)
+ std::abort ();
+
+ return 1;
+}
+
+int
+main (int argc, char **argv)
+{
+ static int foo = get_foo ();
+ return 0;
+}
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