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gthr-posix.h (__gthread_cond_broadcast, [...]): Add to extend interface for POSIX conditional variables.

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2007-09-13  Doug Kwan  <dougkwan@google.com>

        * gcc/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.
        * gcc/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.
        * gcc/gthr-single.h (__gthread_cond_broadcast, __gthread_cond_wait,
        __gthread_cond_wait_recursive): Add to extend interface for POSIX
        conditional variables.
        * gcc/gthr.h: Update comments to document new interface.
        * libstdc++-v3/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.
        * 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.

From-SVN: r129030
This commit is contained in:
Doug Kwan 2007-10-05 05:35:46 +00:00 committed by Jason Merrill
parent 90e965bb84
commit afd82ef5ab
9 changed files with 455 additions and 44 deletions
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15
gcc/ChangeLog
View File

@ -1,3 +1,18 @@
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.
2007-10-04 Geoffrey Keating <geoffk@apple.com>
* cgraphunit.c (cgraph_build_static_cdtor): Don't set

33
gcc/gthr-posix.h
View File

@ -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_recursive_mutex_t;
#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 (__gthread_recursive_mutex_t *mutex)
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 */

29
gcc/gthr-posix95.h
View File

@ -45,6 +45,11 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
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 (__gthread_recursive_mutex_t *mutex)
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 */

19
gcc/gthr-single.h
View File

@ -251,6 +251,25 @@ __gthread_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex)
return __gthread_mutex_unlock (mutex);
}
static inline int
__gthread_cond_broadcast (__gthread_cond_t cond)
{
return 0;
}
static inline int
__gthread_cond_wait (__gthread_cond_t cond, __gthread_mutex_t *mutex)
{
return 0;
}
static inline int
__gthread_cond_wait_recursive (__gthread_cond_t cond,
__gthread_recursive_mutex_t *mutex)
{
return 0;
}
#endif /* _LIBOBJC */
#undef UNUSED

18
gcc/gthr.h
View File

@ -81,6 +81,24 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
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.

20
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,23 @@
2007-10-04 Doug Kwan <dougkwan@google.com>
* 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.
2007-10-04 Paolo Carlini <pcarlini@suse.de>
* testsuite/23_containers/vector/requirements/dr438/assign_neg.cc:

104
libstdc++-v3/include/ext/concurrence.h
View File

@ -81,6 +81,22 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
{ return "__gnu_cxx::__concurrence_unlock_error"; }
};
class __concurrence_broadcast_error : public std::exception
{
public:
virtual char const*
what() const throw()
{ return "__gnu_cxx::__concurrence_broadcast_error"; }
};
class __concurrence_wait_error : public std::exception
{
public:
virtual char const*
what() const throw()
{ return "__gnu_cxx::__concurrence_wait_error"; }
};
// Substitute for concurrence_error object in the case of -fno-exceptions.
inline void
__throw_concurrence_lock_error()
@ -102,6 +118,28 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
#endif
}
#ifdef __GTHREAD_HAS_COND
inline void
__throw_concurrence_broadcast_error()
{
#if __EXCEPTIONS
throw __concurrence_broadcast_error();
#else
__builtin_abort();
#endif
}
inline void
__throw_concurrence_wait_error()
{
#if __EXCEPTIONS
throw __concurrence_wait_error();
#else
__builtin_abort();
#endif
}
#endif
class __mutex
{
private:
@ -147,6 +185,9 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
}
#endif
}
__gthread_mutex_t* gthread_mutex(void)
{ return &_M_mutex; }
};
class __recursive_mutex
@ -194,6 +235,9 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
}
#endif
}
__gthread_recursive_mutex_t* gthread_recursive_mutex(void)
{ return &_M_mutex; }
};
/// @brief Scoped lock idiom.
@ -218,6 +262,66 @@ _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
{ _M_device.unlock(); }
};
#ifdef __GTHREAD_HAS_COND
class __cond
{
private:
__gthread_cond_t _M_cond;
__cond(const __cond&);
__cond& operator=(const __cond&);
public:
__cond()
{
#if __GTHREADS
if (__gthread_active_p())
{
#if defined __GTHREAD_COND_INIT
__gthread_cond_t __tmp = __GTHREAD_COND_INIT;
_M_cond = __tmp;
#else
__GTHREAD_MUTEX_INIT_FUNCTION(&_M_cond);
#endif
}
#endif
}
void broadcast()
{
#if __GTHREADS
if (__gthread_active_p())
{
if (__gthread_cond_broadcast(&_M_cond) != 0)
__throw_concurrence_broadcast_error();
}
#endif
}
void wait(__mutex *mutex)
{
#if __GTHREADS
{
if (__gthread_cond_wait(&_M_cond, mutex->gthread_mutex()) != 0)
__throw_concurrence_wait_error();
}
#endif
}
void wait_recursive(__recursive_mutex *mutex)
{
#if __GTHREADS
{
if (__gthread_cond_wait_recursive(&_M_cond,
mutex->gthread_recursive_mutex())
!= 0)
__throw_concurrence_wait_error();
}
#endif
}
};
#endif
_GLIBCXX_END_NAMESPACE
#endif

194
libstdc++-v3/libsupc++/guard.cc
View File

@ -62,6 +62,28 @@ namespace
}
}
namespace
{
// A single conditional variable controlling all static initializations.
static __gnu_cxx::__cond* static_cond;
// using a fake type to avoid initializing a static class.
typedef char fake_cond_t[sizeof(__gnu_cxx::__cond)]
__attribute__ ((aligned(__alignof__(__gnu_cxx::__cond))));
fake_cond_t fake_cond;
static void init_static_cond()
{ static_cond = new (&fake_cond) __gnu_cxx::__cond(); }
__gnu_cxx::__cond&
get_static_cond()
{
static __gthread_once_t once = __GTHREAD_ONCE_INIT;
__gthread_once(&once, init_static_cond);
return *static_cond;
}
}
#ifndef _GLIBCXX_GUARD_TEST_AND_ACQUIRE
inline bool
__test_and_acquire (__cxxabiv1::__guard *g)
@ -110,34 +132,87 @@ namespace __gnu_cxx
recursive_init_error::~recursive_init_error() 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 (__guard *g)
static inline void
throw_recursive_init_exception()
{
if (_GLIBCXX_GUARD_TEST (g))
return 0;
if (recursion_push (g))
{
#ifdef __EXCEPTIONS
throw __gnu_cxx::recursive_init_error();
#else
// Use __builtin_trap so we don't require abort().
__builtin_trap ();
__builtin_trap();
#endif
}
}
// acuire() is a helper function used to acquire guard if thread support is
// not compiled in or is compiled in but not enabled at run-time.
static int
acquire(__guard *g)
{
// Quit if the object is already initialized.
if (_GLIBCXX_GUARD_TEST(g))
return 0;
if (init_in_progress_flag(g))
throw_recursive_init_exception();
set_init_in_progress_flag(g, 1);
return 1;
}
// Simple wrapper for exception safety.
struct mutex_wrapper
{
#ifdef __GTHREADS
bool unlock;
mutex_wrapper() : unlock(true)
{ get_static_mutex().lock(); }
~mutex_wrapper()
{
if (unlock)
static_mutex->unlock();
}
#endif
};
extern "C"
int __cxa_guard_acquire (__guard *g)
{
@ -150,28 +225,39 @@ namespace __cxxabiv1
if (__gthread_active_p ())
{
// Simple wrapper for exception safety.
struct mutex_wrapper
{
bool unlock;
mutex_wrapper() : unlock(true)
{ get_static_mutex().lock(); }
~mutex_wrapper()
{
if (unlock)
static_mutex->unlock();
}
};
mutex_wrapper mw;
if (acquire (g))
{
mw.unlock = false;
return 1;
}
return 0;
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.
get_static_cond().wait_recursive(&get_static_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(g))
{
mw.unlock = false;
return 1; // The mutex still locked.
}
return 0; // The mutex will be unlocked via wrapper.
#endif
}
}
#endif
@ -181,8 +267,24 @@ 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.
get_static_cond().broadcast();
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
@ -191,10 +293,26 @@ 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);
get_static_cond().broadcast();
return;
}
#endif
set_init_in_progress_flag(g, 0);
_GLIBCXX_GUARD_SET_AND_RELEASE (g);
#ifdef __GTHREADS
if (__gthread_active_p ())
#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
}

67
libstdc++-v3/testsuite/thread/guard.cc Normal file
View File

@ -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;
}