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support for multithread-safe libraries
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From: |
Bruno Haible |
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Subject: |
support for multithread-safe libraries |
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Date: |
Thu, 14 Jul 2005 16:10:14 +0200 |
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User-agent: |
KMail/1.5 |
Hi,
When you write a library which should be multithread-safe but needs some
global data (such as hash tables used as caches), you need some locking.
Problems are:
1. Your library should not become dependent on pthread, because in many
situations it will be used in single-threaded programs.
2. You don't even know which thread library the application will be
using. It may be POSIX threads. Or GNU Pth. Or the old Solaris threads.
But you don't want to clutter your library's code with lots of #ifdefs.
I propose to add a new module 'lock' to gnulib. It addresses these problems.
It will be used in gettext 0.15.
Bruno
=============================== modules/lock ==================================
Description:
Locking in multithreaded situations.
Files:
lib/lock.h
lib/lock.c
m4/lock.m4
m4/lib-ld.m4
m4/lib-link.m4
m4/lib-prefix.m4
build-aux/config.rpath
Depends-on:
configure.ac:
gl_LOCK
Makefile.am:
lib_SOURCES += lock.h lock.c
Include:
"lock.h"
License:
LGPL
Maintainer:
Bruno Haible
=============================== lib/lock.h ====================================
/* Locking in multithreaded situations.
Copyright (C) 2005 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU Library General Public License as published
by the Free Software Foundation; either version 2, or (at your option)
any later version.
This program 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
USA. */
/* Written by Bruno Haible <address@hidden>, 2005.
Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
gthr-win32.h. */
/* This file contains locking primitives for use with a given thread library.
It does not contain primitives for creating threads or for other
synchronization primitives.
Normal (non-recursive) locks:
Type: gl_lock_t
Declaration: gl_lock_define(extern, name)
Initializer: gl_lock_define_initialized(, name)
Initialization: gl_lock_init (name);
Taking the lock: gl_lock_lock (name);
Releasing the lock: gl_lock_unlock (name);
De-initialization: gl_lock_destroy (name);
Read-Write (non-recursive) locks:
Type: gl_rwlock_t
Declaration: gl_rwlock_define(extern, name)
Initializer: gl_rwlock_define_initialized(, name)
Initialization: gl_rwlock_init (name);
Taking the lock: gl_rwlock_rdlock (name);
gl_rwlock_wrlock (name);
Releasing the lock: gl_rwlock_unlock (name);
De-initialization: gl_rwlock_destroy (name);
Recursive locks:
Type: gl_recursive_lock_t
Declaration: gl_recursive_lock_define(extern, name)
Initializer: gl_recursive_lock_define_initialized(, name)
Initialization: gl_recursive_lock_init (name);
Taking the lock: gl_recursive_lock_lock (name);
Releasing the lock: gl_recursive_lock_unlock (name);
De-initialization: gl_recursive_lock_destroy (name);
*/
/* ========================================================================= */
#if USE_POSIX_THREADS
/* Use the POSIX threads library. */
# include <pthread.h>
# include <stdlib.h>
# if USE_POSIX_THREADS_WEAK
/* Use weak references to the POSIX threads library. */
/* Weak references avoid dragging in external libraries if the other parts
of the program don't use them. Here we use them, because we don't want
every program that uses libintl to depend on libpthread. This assumes
that libpthread would not be loaded after libintl; i.e. if libintl is
loaded first, by an executable that does not depend on libpthread, and
then a module is dynamically loaded that depends on libpthread, libintl
will not be multithread-safe. */
/* The way to test at runtime whether libpthread is present is to test
whether a function pointer's value, such as &pthread_mutex_init, is
non-NULL. However, some versions of GCC have a bug through which, in
PIC mode, &foo != NULL always evaluates to true if there is a direct
call to foo(...) in the same function. To avoid this, we test the
address of a function in libpthread that we don't use. */
# pragma weak pthread_mutex_init
# pragma weak pthread_mutex_lock
# pragma weak pthread_mutex_unlock
# pragma weak pthread_rwlock_init
# pragma weak pthread_rwlock_rdlock
# pragma weak pthread_rwlock_wrlock
# pragma weak pthread_rwlock_unlock
# pragma weak pthread_mutexattr_init
# pragma weak pthread_mutexattr_settype
# pragma weak pthread_mutexattr_destroy
# ifndef pthread_self
# pragma weak pthread_self
# endif
# pragma weak pthread_cancel
# define pthread_in_use() (pthread_cancel != NULL)
# else
# define pthread_in_use() 1
# endif
/* -------------------------- gl_lock_t datatype -------------------------- */
typedef pthread_mutex_t gl_lock_t;
# define gl_lock_define(STORAGECLASS, NAME) \
STORAGECLASS pthread_mutex_t NAME;
# define gl_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pthread_mutex_t NAME = PTHREAD_MUTEX_INITIALIZER;
# define gl_lock_init(NAME) \
if (pthread_in_use () && pthread_mutex_init (&NAME, NULL) != 0) abort ()
# define gl_lock_lock(NAME) \
if (pthread_in_use () && pthread_mutex_lock (&NAME) != 0) abort ()
# define gl_lock_unlock(NAME) \
if (pthread_in_use () && pthread_mutex_unlock (&NAME) != 0) abort ()
# define gl_lock_destroy(NAME) \
if (pthread_in_use () && pthread_mutex_destroy (&NAME) != 0) abort ()
/* ------------------------- gl_rwlock_t datatype ------------------------- */
# if HAVE_PTHREAD_RWLOCK
# ifdef PTHREAD_RWLOCK_INITIALIZER
typedef pthread_rwlock_t gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME) \
STORAGECLASS pthread_rwlock_t NAME;
# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pthread_rwlock_t NAME = PTHREAD_RWLOCK_INITIALIZER;
# define gl_rwlock_init(NAME) \
if (pthread_in_use () && pthread_rwlock_init (&NAME, NULL) != 0) abort ()
# define gl_rwlock_rdlock(NAME) \
if (pthread_in_use () && pthread_rwlock_rdlock (&NAME) != 0) abort ()
# define gl_rwlock_wrlock(NAME) \
if (pthread_in_use () && pthread_rwlock_wrlock (&NAME) != 0) abort ()
# define gl_rwlock_unlock(NAME) \
if (pthread_in_use () && pthread_rwlock_unlock (&NAME) != 0) abort ()
# define gl_rwlock_destroy(NAME) \
if (pthread_in_use () && pthread_rwlock_destroy (&NAME) != 0) abort ()
# else
typedef struct
{
int initialized;
pthread_mutex_t guard; /* protects the initialization */
pthread_rwlock_t rwlock; /* read-write lock */
}
gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_rwlock_t NAME;
# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_rwlock_t NAME = { 0, PTHREAD_MUTEX_INITIALIZER };
# define gl_rwlock_init(NAME) \
if (pthread_in_use ()) glthread_rwlock_init (&NAME)
# define gl_rwlock_rdlock(NAME) \
if (pthread_in_use ()) glthread_rwlock_rdlock (&NAME)
# define gl_rwlock_wrlock(NAME) \
if (pthread_in_use ()) glthread_rwlock_wrlock (&NAME)
# define gl_rwlock_unlock(NAME) \
if (pthread_in_use ()) glthread_rwlock_unlock (&NAME)
# define gl_rwlock_destroy(NAME) \
if (pthread_in_use ()) glthread_rwlock_destroy (&NAME)
extern void glthread_rwlock_init (gl_rwlock_t *lock);
extern void glthread_rwlock_rdlock (gl_rwlock_t *lock);
extern void glthread_rwlock_wrlock (gl_rwlock_t *lock);
extern void glthread_rwlock_unlock (gl_rwlock_t *lock);
extern void glthread_rwlock_destroy (gl_rwlock_t *lock);
# endif
# else
typedef struct
{
pthread_mutex_t lock; /* protects the remaining fields */
pthread_cond_t waiting_readers; /* waiting readers */
pthread_cond_t waiting_writers; /* waiting writers */
unsigned int waiting_writers_count; /* number of waiting writers */
int runcount; /* number of readers running, or -1 when a writer runs
*/
}
gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_rwlock_t NAME;
# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_rwlock_t NAME = \
{ PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER,
PTHREAD_COND_INITIALIZER, 0, 0 };
# define gl_rwlock_init(NAME) \
if (pthread_in_use ()) glthread_rwlock_init (&NAME)
# define gl_rwlock_rdlock(NAME) \
if (pthread_in_use ()) glthread_rwlock_rdlock (&NAME)
# define gl_rwlock_wrlock(NAME) \
if (pthread_in_use ()) glthread_rwlock_wrlock (&NAME)
# define gl_rwlock_unlock(NAME) \
if (pthread_in_use ()) glthread_rwlock_unlock (&NAME)
# define gl_rwlock_destroy(NAME) \
if (pthread_in_use ()) glthread_rwlock_destroy (&NAME)
extern void glthread_rwlock_init (gl_rwlock_t *lock);
extern void glthread_rwlock_rdlock (gl_rwlock_t *lock);
extern void glthread_rwlock_wrlock (gl_rwlock_t *lock);
extern void glthread_rwlock_unlock (gl_rwlock_t *lock);
extern void glthread_rwlock_destroy (gl_rwlock_t *lock);
# endif
/* --------------------- gl_recursive_lock_t datatype --------------------- */
# if HAVE_PTHREAD_MUTEX_RECURSIVE
# if defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER || defined
PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
typedef pthread_mutex_t gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME) \
STORAGECLASS pthread_mutex_t NAME;
# ifdef PTHREAD_RECURSIVE_MUTEX_INITIALIZER
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pthread_mutex_t NAME = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
# else
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pthread_mutex_t NAME =
PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
# endif
# define gl_recursive_lock_init(NAME) \
if (pthread_in_use () && pthread_mutex_init (&NAME, NULL) != 0) abort ()
# define gl_recursive_lock_lock(NAME) \
if (pthread_in_use () && pthread_mutex_lock (&NAME) != 0) abort ()
# define gl_recursive_lock_unlock(NAME) \
if (pthread_in_use () && pthread_mutex_unlock (&NAME) != 0) abort ()
# define gl_recursive_lock_destroy(NAME) \
if (pthread_in_use () && pthread_mutex_destroy (&NAME) != 0) abort ()
# else
typedef struct
{
pthread_mutex_t recmutex; /* recursive mutex */
pthread_mutex_t guard; /* protects the initialization */
int initialized;
}
gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME;
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME = \
{ PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, 0 };
# define gl_recursive_lock_init(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_init (&NAME)
# define gl_recursive_lock_lock(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_lock (&NAME)
# define gl_recursive_lock_unlock(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_unlock (&NAME)
# define gl_recursive_lock_destroy(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_destroy (&NAME)
extern void glthread_recursive_lock_init (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_lock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_unlock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_destroy (gl_recursive_lock_t *lock);
# endif
# else
/* Old versions of POSIX threads on Solaris did not have recursive locks.
We have to implement them ourselves. */
typedef struct
{
pthread_mutex_t mutex;
pthread_t owner;
unsigned long depth;
}
gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME;
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME = \
{ PTHREAD_MUTEX_INITIALIZER, (pthread_t) 0, 0 };
# define gl_recursive_lock_init(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_init (&NAME)
# define gl_recursive_lock_lock(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_lock (&NAME)
# define gl_recursive_lock_unlock(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_unlock (&NAME)
# define gl_recursive_lock_destroy(NAME) \
if (pthread_in_use ()) glthread_recursive_lock_destroy (&NAME)
extern void glthread_recursive_lock_init (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_lock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_unlock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_destroy (gl_recursive_lock_t *lock);
# endif
#endif
/* ========================================================================= */
#if USE_PTH_THREADS
/* Use the GNU Pth threads library. */
# include <pth.h>
# include <stdlib.h>
# if USE_PTH_THREADS_WEAK
/* Use weak references to the GNU Pth threads library. */
# pragma weak pth_mutex_init
# pragma weak pth_mutex_acquire
# pragma weak pth_mutex_release
# pragma weak pth_rwlock_init
# pragma weak pth_rwlock_acquire
# pragma weak pth_rwlock_release
# pragma weak pth_cancel
# define pth_in_use() (pth_cancel != NULL)
# else
# define pth_in_use() 1
# endif
/* -------------------------- gl_lock_t datatype -------------------------- */
typedef pth_mutex_t gl_lock_t;
# define gl_lock_define(STORAGECLASS, NAME) \
STORAGECLASS pth_mutex_t NAME;
# define gl_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pth_mutex_t NAME = PTH_MUTEX_INIT;
# define gl_lock_init(NAME) \
if (pth_in_use() && !pth_mutex_init (&NAME)) abort ()
# define gl_lock_lock(NAME) \
if (pth_in_use() && !pth_mutex_acquire (&NAME, 0, NULL)) abort ()
# define gl_lock_unlock(NAME) \
if (pth_in_use() && !pth_mutex_release (&NAME)) abort ()
# define gl_lock_destroy(NAME) \
(void)(&NAME)
/* ------------------------- gl_rwlock_t datatype ------------------------- */
typedef pth_rwlock_t gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME) \
STORAGECLASS pth_rwlock_t NAME;
# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pth_rwlock_t NAME = PTH_RWLOCK_INIT;
# define gl_rwlock_init(NAME) \
if (pth_in_use() && !pth_rwlock_init (&NAME)) abort ()
# define gl_rwlock_rdlock(NAME) \
if (pth_in_use() && !pth_rwlock_acquire (&NAME, PTH_RWLOCK_RD, 0, NULL))
abort ()
# define gl_rwlock_wrlock(NAME) \
if (pth_in_use() && !pth_rwlock_acquire (&NAME, PTH_RWLOCK_RW, 0, NULL))
abort ()
# define gl_rwlock_unlock(NAME) \
if (pth_in_use() && !pth_rwlock_release (&NAME)) abort ()
# define gl_rwlock_destroy(NAME) \
(void)(&NAME)
/* --------------------- gl_recursive_lock_t datatype --------------------- */
/* In Pth, mutexes are recursive by default. */
typedef pth_mutex_t gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME) \
STORAGECLASS pth_mutex_t NAME;
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS pth_mutex_t NAME = PTH_MUTEX_INIT;
# define gl_recursive_lock_init(NAME) \
if (pth_in_use() && !pth_mutex_init (&NAME)) abort ()
# define gl_recursive_lock_lock(NAME) \
if (pth_in_use() && !pth_mutex_acquire (&NAME, 0, NULL)) abort ()
# define gl_recursive_lock_unlock(NAME) \
if (pth_in_use() && !pth_mutex_release (&NAME)) abort ()
# define gl_recursive_lock_destroy(NAME) \
(void)(&NAME)
#endif
/* ========================================================================= */
#if USE_SOLARIS_THREADS
/* Use the old Solaris threads library. */
# include <thread.h>
# include <synch.h>
# include <stdlib.h>
# if USE_SOLARIS_THREADS_WEAK
/* Use weak references to the old Solaris threads library. */
# pragma weak mutex_init
# pragma weak mutex_lock
# pragma weak mutex_unlock
# pragma weak rwlock_init
# pragma weak rw_rdlock
# pragma weak rw_wrlock
# pragma weak rw_unlock
# pragma weak thr_self
# pragma weak thr_suspend
# define thread_in_use() (thr_suspend != NULL)
# else
# define thread_in_use() 1
# endif
/* -------------------------- gl_lock_t datatype -------------------------- */
typedef mutex_t gl_lock_t;
# define gl_lock_define(STORAGECLASS, NAME) \
STORAGECLASS mutex_t NAME;
# define gl_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS mutex_t NAME = DEFAULTMUTEX;
# define gl_lock_init(NAME) \
if (thread_in_use () && mutex_init (&NAME, USYNC_THREAD, NULL) != 0) abort
()
# define gl_lock_lock(NAME) \
if (thread_in_use () && mutex_lock (&NAME) != 0) abort ()
# define gl_lock_unlock(NAME) \
if (thread_in_use () && mutex_unlock (&NAME) != 0) abort ()
# define gl_lock_destroy(NAME) \
if (thread_in_use () && mutex_destroy (&NAME) != 0) abort ()
/* ------------------------- gl_rwlock_t datatype ------------------------- */
typedef rwlock_t gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME) \
STORAGECLASS rwlock_t NAME;
# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS rwlock_t NAME = DEFAULTRWLOCK;
# define gl_rwlock_init(NAME) \
if (thread_in_use () && rwlock_init (&NAME, USYNC_THREAD, NULL) != 0) abort
()
# define gl_rwlock_rdlock(NAME) \
if (thread_in_use () && rw_rdlock (&NAME) != 0) abort ()
# define gl_rwlock_wrlock(NAME) \
if (thread_in_use () && rw_wrlock (&NAME) != 0) abort ()
# define gl_rwlock_unlock(NAME) \
if (thread_in_use () && rw_unlock (&NAME) != 0) abort ()
# define gl_rwlock_destroy(NAME) \
if (thread_in_use () && rwlock_destroy (&NAME) != 0) abort ()
/* --------------------- gl_recursive_lock_t datatype --------------------- */
/* Old Solaris threads did not have recursive locks.
We have to implement them ourselves. */
typedef struct
{
mutex_t mutex;
thread_t owner;
unsigned long depth;
}
gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME;
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME = { DEFAULTMUTEX, (thread_t) 0, 0 };
# define gl_recursive_lock_init(NAME) \
if (thread_in_use ()) glthread_recursive_lock_init (&NAME)
# define gl_recursive_lock_lock(NAME) \
if (thread_in_use ()) glthread_recursive_lock_lock (&NAME)
# define gl_recursive_lock_unlock(NAME) \
if (thread_in_use ()) glthread_recursive_lock_unlock (&NAME)
# define gl_recursive_lock_destroy(NAME) \
if (thread_in_use ()) glthread_recursive_lock_destroy (&NAME)
extern void glthread_recursive_lock_init (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_lock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_unlock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_destroy (gl_recursive_lock_t *lock);
#endif
/* ========================================================================= */
#if USE_WIN32_THREADS
# include <windows.h>
/* We can use CRITICAL_SECTION directly, rather than the Win32 Event, Mutex,
Semaphore types, because
- we need only to synchronize inside a single process (address space),
not inter-process locking,
- we don't need to support trylock operations. (TryEnterCriticalSection
does not work on Windows 95/98/ME. Packages that need trylock usually
define their own mutex type.) */
/* There is no way to statically initialize a CRITICAL_SECTION. It needs
to be done lazily, once only. For this we need spinlocks. */
typedef struct { volatile int done; volatile long started; } gl_spinlock_t;
/* -------------------------- gl_lock_t datatype -------------------------- */
typedef struct
{
gl_spinlock_t guard; /* protects the initialization */
CRITICAL_SECTION lock;
}
gl_lock_t;
# define gl_lock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_lock_t NAME;
# define gl_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_lock_t NAME = { { 0, -1 } };
# define gl_lock_init(NAME) \
glthread_lock_init (&NAME)
# define gl_lock_lock(NAME) \
glthread_lock_lock (&NAME)
# define gl_lock_unlock(NAME) \
glthread_lock_unlock (&NAME)
# define gl_lock_destroy(NAME) \
glthread_lock_destroy (&NAME)
extern void glthread_lock_init (gl_lock_t *lock);
extern void glthread_lock_lock (gl_lock_t *lock);
extern void glthread_lock_unlock (gl_lock_t *lock);
extern void glthread_lock_destroy (gl_lock_t *lock);
/* ------------------------- gl_rwlock_t datatype ------------------------- */
/* It is impossible to implement read-write locks using plain locks, without
introducing an extra thread dedicated to managing read-write locks.
Therefore here we need to use the low-level Event type. */
typedef struct
{
HANDLE *array; /* array of waiting threads, each represented by an
event */
unsigned int count; /* number of waiting threads */
unsigned int alloc; /* length of allocated array */
unsigned int offset; /* index of first waiting thread in array */
}
gl_waitqueue_t;
typedef struct
{
gl_spinlock_t guard; /* protects the initialization */
CRITICAL_SECTION lock; /* protects the remaining fields */
gl_waitqueue_t waiting_readers; /* waiting readers */
gl_waitqueue_t waiting_writers; /* waiting writers */
int runcount; /* number of readers running, or -1 when a writer runs
*/
}
gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_rwlock_t NAME;
# define gl_rwlock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_rwlock_t NAME = { { 0, -1 } };
# define gl_rwlock_init(NAME) \
glthread_rwlock_init (&NAME)
# define gl_rwlock_rdlock(NAME) \
glthread_rwlock_rdlock (&NAME)
# define gl_rwlock_wrlock(NAME) \
glthread_rwlock_wrlock (&NAME)
# define gl_rwlock_unlock(NAME) \
glthread_rwlock_unlock (&NAME)
# define gl_rwlock_destroy(NAME) \
glthread_rwlock_destroy (&NAME)
extern void glthread_rwlock_init (gl_rwlock_t *lock);
extern void glthread_rwlock_rdlock (gl_rwlock_t *lock);
extern void glthread_rwlock_wrlock (gl_rwlock_t *lock);
extern void glthread_rwlock_unlock (gl_rwlock_t *lock);
extern void glthread_rwlock_destroy (gl_rwlock_t *lock);
/* --------------------- gl_recursive_lock_t datatype --------------------- */
/* The Win32 documentation says that CRITICAL_SECTION already implements a
recursive lock. But we need not rely on it: It's easy to implement a
recursive lock without this assumption. */
typedef struct
{
gl_spinlock_t guard; /* protects the initialization */
DWORD owner;
unsigned long depth;
CRITICAL_SECTION lock;
}
gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME;
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME) \
STORAGECLASS gl_recursive_lock_t NAME = { { 0, -1 }, INVALID_HANDLE_VALUE,
0 };
# define gl_recursive_lock_init(NAME) \
glthread_recursive_lock_init (&NAME)
# define gl_recursive_lock_lock(NAME) \
glthread_recursive_lock_lock (&NAME)
# define gl_recursive_lock_unlock(NAME) \
glthread_recursive_lock_unlock (&NAME)
# define gl_recursive_lock_destroy(NAME) \
glthread_recursive_lock_destroy (&NAME)
extern void glthread_recursive_lock_init (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_lock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_unlock (gl_recursive_lock_t *lock);
extern void glthread_recursive_lock_destroy (gl_recursive_lock_t *lock);
#endif
/* ========================================================================= */
#if !(USE_POSIX_THREADS || USE_PTH_THREADS || USE_SOLARIS_THREADS ||
USE_WIN32_THREADS)
/* Provide dummy implementation if threads are not supported. */
/* -------------------------- gl_lock_t datatype -------------------------- */
typedef int gl_lock_t;
# define gl_lock_define(STORAGECLASS, NAME)
# define gl_lock_define_initialized(STORAGECLASS, NAME)
# define gl_lock_init(NAME)
# define gl_lock_lock(NAME)
# define gl_lock_unlock(NAME)
/* ------------------------- gl_rwlock_t datatype ------------------------- */
typedef int gl_rwlock_t;
# define gl_rwlock_define(STORAGECLASS, NAME)
# define gl_rwlock_define_initialized(STORAGECLASS, NAME)
# define gl_rwlock_init(NAME)
# define gl_rwlock_rdlock(NAME)
# define gl_rwlock_wrlock(NAME)
# define gl_rwlock_unlock(NAME)
/* --------------------- gl_recursive_lock_t datatype --------------------- */
typedef int gl_recursive_lock_t;
# define gl_recursive_lock_define(STORAGECLASS, NAME)
# define gl_recursive_lock_define_initialized(STORAGECLASS, NAME)
# define gl_recursive_lock_init(NAME)
# define gl_recursive_lock_lock(NAME)
# define gl_recursive_lock_unlock(NAME)
#endif
=============================== lib/lock.c ====================================
/* Locking in multithreaded situations.
Copyright (C) 2005 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU Library General Public License as published
by the Free Software Foundation; either version 2, or (at your option)
any later version.
This program 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
USA. */
/* Written by Bruno Haible <address@hidden>, 2005.
Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
gthr-win32.h. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "lock.h"
/* ========================================================================= */
#if USE_POSIX_THREADS
/* Use the POSIX threads library. */
/* -------------------------- gl_lock_t datatype -------------------------- */
/* ------------------------- gl_rwlock_t datatype ------------------------- */
# if HAVE_PTHREAD_RWLOCK
# if !defined PTHREAD_RWLOCK_INITIALIZER
void
glthread_rwlock_init (gl_rwlock_t *lock)
{
if (pthread_rwlock_init (&lock->rwlock, NULL) != 0)
abort ();
lock->initialized = 1;
}
void
glthread_rwlock_rdlock (gl_rwlock_t *lock)
{
if (!lock->initialized)
{
if (pthread_mutex_lock (&lock->guard) != 0)
abort ();
if (!lock->initialized)
glthread_rwlock_init (lock);
if (pthread_mutex_unlock (&lock->guard) != 0)
abort ();
}
if (pthread_rwlock_rdlock (&lock->rwlock) != 0)
abort ();
}
void
glthread_rwlock_wrlock (gl_rwlock_t *lock)
{
if (!lock->initialized)
{
if (pthread_mutex_lock (&lock->guard) != 0)
abort ();
if (!lock->initialized)
glthread_rwlock_init (lock);
if (pthread_mutex_unlock (&lock->guard) != 0)
abort ();
}
if (pthread_rwlock_wrlock (&lock->rwlock) != 0)
abort ();
}
void
glthread_rwlock_unlock (gl_rwlock_t *lock)
{
if (!lock->initialized)
abort ();
if (pthread_rwlock_unlock (&lock->rwlock) != 0)
abort ();
}
void
glthread_rwlock_destroy (gl_rwlock_t *lock)
{
if (!lock->initialized)
abort ();
if (pthread_rwlock_destroy (&lock->rwlock) != 0)
abort ();
lock->initialized = 0;
}
# endif
# else
void
glthread_rwlock_init (gl_rwlock_t *lock)
{
if (pthread_mutex_init (&lock->lock, NULL) != 0)
abort ();
if (pthread_cond_init (&lock->waiting_readers, NULL) != 0)
abort ();
if (pthread_cond_init (&lock->waiting_writers, NULL) != 0)
abort ();
lock->waiting_writers_count = 0;
lock->runcount = 0;
}
void
glthread_rwlock_rdlock (gl_rwlock_t *lock)
{
if (pthread_mutex_lock (&lock->lock) != 0)
abort ();
/* Test whether only readers are currently running, and whether the runcount
field will not overflow. */
/* POSIX says: "It is implementation-defined whether the calling thread
acquires the lock when a writer does not hold the lock and there are
writers blocked on the lock." Let's say, no: give the writers a higher
priority. */
while (!(lock->runcount + 1 > 0 && lock->waiting_writers_count == 0))
{
/* This thread has to wait for a while. Enqueue it among the
waiting_readers. */
if (pthread_cond_wait (&lock->waiting_readers, &lock->lock) != 0)
abort ();
}
lock->runcount++;
if (pthread_mutex_unlock (&lock->lock) != 0)
abort ();
}
void
glthread_rwlock_wrlock (gl_rwlock_t *lock)
{
if (pthread_mutex_lock (&lock->lock) != 0)
abort ();
/* Test whether no readers or writers are currently running. */
while (!(lock->runcount == 0))
{
/* This thread has to wait for a while. Enqueue it among the
waiting_writers. */
lock->waiting_writers_count++;
if (pthread_cond_wait (&lock->waiting_writers, &lock->lock) != 0)
abort ();
lock->waiting_writers_count--;
}
lock->runcount--; /* runcount becomes -1 */
if (pthread_mutex_unlock (&lock->lock) != 0)
abort ();
}
void
glthread_rwlock_unlock (gl_rwlock_t *lock)
{
if (pthread_mutex_lock (&lock->lock) != 0)
abort ();
if (lock->runcount < 0)
{
/* Drop a writer lock. */
if (!(lock->runcount == -1))
abort ();
lock->runcount = 0;
}
else
{
/* Drop a reader lock. */
if (!(lock->runcount > 0))
abort ();
lock->runcount--;
}
if (lock->runcount == 0)
{
/* POSIX recommends that "write locks shall take precedence over read
locks", to avoid "writer starvation". */
if (lock->waiting_writers_count > 0)
{
/* Wake up one of the waiting writers. */
if (pthread_cond_signal (&lock->waiting_writers) != 0)
abort ();
}
else
{
/* Wake up all waiting readers. */
if (pthread_cond_broadcast (&lock->waiting_readers) != 0)
abort ();
}
}
if (pthread_mutex_unlock (&lock->lock) != 0)
abort ();
}
void
glthread_rwlock_destroy (gl_rwlock_t *lock)
{
if (pthread_mutex_destroy (&lock->lock) != 0)
abort ();
if (pthread_cond_destroy (&lock->waiting_readers) != 0)
abort ();
if (pthread_cond_destroy (&lock->waiting_writers) != 0)
abort ();
}
# endif
/* --------------------- gl_recursive_lock_t datatype --------------------- */
# if HAVE_PTHREAD_MUTEX_RECURSIVE
# if !(defined PTHREAD_RECURSIVE_MUTEX_INITIALIZER || defined
PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP)
void
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
{
pthread_mutexattr_t attributes;
if (pthread_mutexattr_init (&attributes) != 0)
abort ();
if (pthread_mutexattr_settype (&attributes, PTHREAD_MUTEX_RECURSIVE) != 0)
abort ();
if (pthread_mutex_init (&lock->recmutex, &attributes) != 0)
abort ();
if (pthread_mutexattr_destroy (&attributes) != 0)
abort ();
lock->initialized = 1;
}
void
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
{
if (!lock->initialized)
{
if (pthread_mutex_lock (&lock->guard) != 0)
abort ();
if (!lock->initialized)
glthread_recursive_lock_init (lock);
if (pthread_mutex_unlock (&lock->guard) != 0)
abort ();
}
if (pthread_mutex_lock (&lock->recmutex) != 0)
abort ();
}
void
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
{
if (!lock->initialized)
abort ();
if (pthread_mutex_unlock (&lock->recmutex) != 0)
abort ();
}
void
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
{
if (!lock->initialized)
abort ();
if (pthread_mutex_destroy (&lock->recmutex) != 0)
abort ();
lock->initialized = 0;
}
# endif
# else
void
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
{
if (pthread_mutex_init (&lock->mutex, NULL) != 0)
abort ();
lock->owner = (pthread_t) 0;
lock->depth = 0;
}
void
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
{
pthread_t self = pthread_self ();
if (lock->owner != self)
{
if (pthread_mutex_lock (&lock->mutex) != 0)
abort ();
lock->owner = self;
}
if (++(lock->depth) == 0) /* wraparound? */
abort ();
}
void
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
{
if (lock->owner != pthread_self ())
abort ();
if (lock->depth == 0)
abort ();
if (--(lock->depth) == 0)
{
lock->owner = (pthread_t) 0;
if (pthread_mutex_unlock (&lock->mutex) != 0)
abort ();
}
}
void
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
{
if (lock->owner != (pthread_t) 0)
abort ();
if (pthread_mutex_destroy (&lock->mutex) != 0)
abort ();
}
# endif
#endif
/* ========================================================================= */
#if USE_PTH_THREADS
/* Use the GNU Pth threads library. */
/* -------------------------- gl_lock_t datatype -------------------------- */
/* ------------------------- gl_rwlock_t datatype ------------------------- */
/* --------------------- gl_recursive_lock_t datatype --------------------- */
#endif
/* ========================================================================= */
#if USE_SOLARIS_THREADS
/* Use the old Solaris threads library. */
/* -------------------------- gl_lock_t datatype -------------------------- */
/* ------------------------- gl_rwlock_t datatype ------------------------- */
/* --------------------- gl_recursive_lock_t datatype --------------------- */
void
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
{
if (mutex_init (&lock->mutex, USYNC_THREAD, NULL) != 0)
abort ();
lock->owner = (thread_t) 0;
lock->depth = 0;
}
void
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
{
thread_t self = thr_self ();
if (lock->owner != self)
{
if (mutex_lock (&lock->mutex) != 0)
abort ();
lock->owner = self;
}
if (++(lock->depth) == 0) /* wraparound? */
abort ();
}
void
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
{
if (lock->owner != thr_self ())
abort ();
if (lock->depth == 0)
abort ();
if (--(lock->depth) == 0)
{
lock->owner = (thread_t) 0;
if (mutex_unlock (&lock->mutex) != 0)
abort ();
}
}
void
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
{
if (lock->owner != (thread_t) 0)
abort ();
if (mutex_destroy (&lock->mutex) != 0)
abort ();
}
#endif
/* ========================================================================= */
#if USE_WIN32_THREADS
/* -------------------------- gl_lock_t datatype -------------------------- */
void
glthread_lock_init (gl_lock_t *lock)
{
InitializeCriticalSection (&lock->lock);
lock->guard.done = 1;
}
void
glthread_lock_lock (gl_lock_t *lock)
{
if (!lock->guard.done)
{
if (InterlockedIncrement (&lock->guard.started) == 0)
/* This thread is the first one to need this lock. Initialize it. */
glthread_lock_init (lock);
else
/* Yield the CPU while waiting for another thread to finish
initializing this lock. */
while (!lock->guard.done)
Sleep (0);
}
EnterCriticalSection (&lock->lock);
}
void
glthread_lock_unlock (gl_lock_t *lock)
{
if (!lock->guard.done)
abort ();
LeaveCriticalSection (&lock->lock);
}
void
glthread_lock_destroy (gl_lock_t *lock)
{
if (!lock->guard.done)
abort ();
DeleteCriticalSection (&lock->lock);
lock->guard.done = 0;
}
/* ------------------------- gl_rwlock_t datatype ------------------------- */
static inline void
gl_waitqueue_init (gl_waitqueue_t *wq)
{
wq->array = NULL;
wq->count = 0;
wq->alloc = 0;
wq->offset = 0;
}
/* Enqueues the current thread, represented by an event, in a wait queue.
Returns INVALID_HANDLE_VALUE if an allocation failure occurs. */
static HANDLE
gl_waitqueue_add (gl_waitqueue_t *wq)
{
HANDLE event;
unsigned int index;
if (wq->count == wq->alloc)
{
unsigned int new_alloc = 2 * wq->alloc + 1;
HANDLE *new_array =
(HANDLE *) realloc (wq->array, new_alloc * sizeof (HANDLE));
if (new_array == NULL)
/* No more memory. */
return INVALID_HANDLE_VALUE;
/* Now is a good opportunity to rotate the array so that its contents
starts at offset 0. */
if (wq->offset > 0)
{
unsigned int old_count = wq->count;
unsigned int old_alloc = wq->alloc;
unsigned int old_offset = wq->offset;
unsigned int i;
if (old_offset + old_count > old_alloc)
{
unsigned int limit = old_offset + old_count - old_alloc;
for (i = 0; i < limit; i++)
new_array[old_alloc + i] = new_array[i];
}
for (i = 0; i < old_count; i++)
new_array[i] = new_array[old_offset + i];
wq->offset = 0;
}
wq->array = new_array;
wq->alloc = new_alloc;
}
event = CreateEvent (NULL, TRUE, FALSE, NULL);
if (event == INVALID_HANDLE_VALUE)
/* No way to allocate an event. */
return INVALID_HANDLE_VALUE;
index = wq->offset + wq->count;
if (index >= wq->alloc)
index -= wq->alloc;
wq->array[index] = event;
wq->count++;
return event;
}
/* Notifies the first thread from a wait queue and dequeues it. */
static inline void
gl_waitqueue_notify_first (gl_waitqueue_t *wq)
{
SetEvent (wq->array[wq->offset + 0]);
wq->offset++;
wq->count--;
if (wq->count == 0 || wq->offset == wq->alloc)
wq->offset = 0;
}
/* Notifies all threads from a wait queue and dequeues them all. */
static inline void
gl_waitqueue_notify_all (gl_waitqueue_t *wq)
{
unsigned int i;
for (i = 0; i < wq->count; i++)
{
unsigned int index = wq->offset + i;
if (index >= wq->alloc)
index -= wq->alloc;
SetEvent (wq->array[index]);
}
wq->count = 0;
wq->offset = 0;
}
void
glthread_rwlock_init (gl_rwlock_t *lock)
{
InitializeCriticalSection (&lock->lock);
gl_waitqueue_init (&lock->waiting_readers);
gl_waitqueue_init (&lock->waiting_writers);
lock->runcount = 0;
lock->guard.done = 1;
}
void
glthread_rwlock_rdlock (gl_rwlock_t *lock)
{
if (!lock->guard.done)
{
if (InterlockedIncrement (&lock->guard.started) == 0)
/* This thread is the first one to need this lock. Initialize it. */
glthread_rwlock_init (lock);
else
/* Yield the CPU while waiting for another thread to finish
initializing this lock. */
while (!lock->guard.done)
Sleep (0);
}
EnterCriticalSection (&lock->lock);
/* Test whether only readers are currently running, and whether the runcount
field will not overflow. */
if (!(lock->runcount + 1 > 0))
{
/* This thread has to wait for a while. Enqueue it among the
waiting_readers. */
HANDLE event = gl_waitqueue_add (&lock->waiting_readers);
if (event != INVALID_HANDLE_VALUE)
{
DWORD result;
LeaveCriticalSection (&lock->lock);
/* Wait until another thread signals this event. */
result = WaitForSingleObject (event, INFINITE);
if (result == WAIT_FAILED || result == WAIT_TIMEOUT)
abort ();
CloseHandle (event);
/* The thread which signalled the event already did the bookkeeping:
removed us from the waiting_readers, incremented lock->runcount.
*/
if (!(lock->runcount > 0))
abort ();
return;
}
else
{
/* Allocation failure. Weird. */
do
{
LeaveCriticalSection (&lock->lock);
Sleep (1);
EnterCriticalSection (&lock->lock);
}
while (!(lock->runcount + 1 > 0));
}
}
lock->runcount++;
LeaveCriticalSection (&lock->lock);
}
void
glthread_rwlock_wrlock (gl_rwlock_t *lock)
{
if (!lock->guard.done)
{
if (InterlockedIncrement (&lock->guard.started) == 0)
/* This thread is the first one to need this lock. Initialize it. */
glthread_rwlock_init (lock);
else
/* Yield the CPU while waiting for another thread to finish
initializing this lock. */
while (!lock->guard.done)
Sleep (0);
}
EnterCriticalSection (&lock->lock);
/* Test whether no readers or writers are currently running. */
if (!(lock->runcount == 0))
{
/* This thread has to wait for a while. Enqueue it among the
waiting_writers. */
HANDLE event = gl_waitqueue_add (&lock->waiting_writers);
if (event != INVALID_HANDLE_VALUE)
{
DWORD result;
LeaveCriticalSection (&lock->lock);
/* Wait until another thread signals this event. */
result = WaitForSingleObject (event, INFINITE);
if (result == WAIT_FAILED || result == WAIT_TIMEOUT)
abort ();
CloseHandle (event);
/* The thread which signalled the event already did the bookkeeping:
removed us from the waiting_writers, set lock->runcount = -1. */
if (!(lock->runcount == -1))
abort ();
return;
}
else
{
/* Allocation failure. Weird. */
do
{
LeaveCriticalSection (&lock->lock);
Sleep (1);
EnterCriticalSection (&lock->lock);
}
while (!(lock->runcount == 0));
}
}
lock->runcount--; /* runcount becomes -1 */
LeaveCriticalSection (&lock->lock);
}
void
glthread_rwlock_unlock (gl_rwlock_t *lock)
{
if (!lock->guard.done)
abort ();
EnterCriticalSection (&lock->lock);
if (lock->runcount < 0)
{
/* Drop a writer lock. */
if (!(lock->runcount == -1))
abort ();
lock->runcount = 0;
}
else
{
/* Drop a reader lock. */
if (!(lock->runcount > 0))
abort ();
lock->runcount--;
}
if (lock->runcount == 0)
{
/* POSIX recommends that "write locks shall take precedence over read
locks", to avoid "writer starvation". */
if (lock->waiting_writers.count > 0)
{
/* Wake up one of the waiting writers. */
lock->runcount--;
gl_waitqueue_notify_first (&lock->waiting_writers);
}
else
{
/* Wake up all waiting readers. */
lock->runcount += lock->waiting_readers.count;
gl_waitqueue_notify_all (&lock->waiting_readers);
}
}
LeaveCriticalSection (&lock->lock);
}
void
glthread_rwlock_destroy (gl_rwlock_t *lock)
{
if (!lock->guard.done)
abort ();
if (lock->runcount != 0)
abort ();
DeleteCriticalSection (&lock->lock);
if (lock->waiting_readers.array != NULL)
free (lock->waiting_readers.array);
if (lock->waiting_writers.array != NULL)
free (lock->waiting_writers.array);
lock->guard.done = 0;
}
/* --------------------- gl_recursive_lock_t datatype --------------------- */
void
glthread_recursive_lock_init (gl_recursive_lock_t *lock)
{
lock->owner = 0;
lock->depth = 0;
InitializeCriticalSection (&lock->lock);
lock->guard.done = 1;
}
void
glthread_recursive_lock_lock (gl_recursive_lock_t *lock)
{
if (!lock->guard.done)
{
if (InterlockedIncrement (&lock->guard.started) == 0)
/* This thread is the first one to need this lock. Initialize it. */
glthread_recursive_lock_init (lock);
else
/* Yield the CPU while waiting for another thread to finish
initializing this lock. */
while (!lock->guard.done)
Sleep (0);
}
{
DWORD self = GetCurrentThreadId ();
if (lock->owner != self)
{
EnterCriticalSection (&lock->lock);
lock->owner = self;
}
if (++(lock->depth) == 0) /* wraparound? */
abort ();
}
}
void
glthread_recursive_lock_unlock (gl_recursive_lock_t *lock)
{
if (lock->owner != GetCurrentThreadId ())
abort ();
if (lock->depth == 0)
abort ();
if (--(lock->depth) == 0)
{
lock->owner = 0;
LeaveCriticalSection (&lock->lock);
}
}
void
glthread_recursive_lock_destroy (gl_recursive_lock_t *lock)
{
if (lock->owner != 0)
abort ();
DeleteCriticalSection (&lock->lock);
lock->guard.done = 0;
}
#endif
/* ========================================================================= */
=============================== lib/lock.m4 ===================================
# lock.m4 serial 1 (gettext-0.15)
dnl Copyright (C) 2005 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl From Bruno Haible.
dnl Tests for a multithreading library to be used.
dnl Defines at most one of the macros USE_POSIX_THREADS, USE_SOLARIS_THREADS,
dnl USE_PTH_THREADS, USE_WIN32_THREADS
dnl Sets the variables LIBTHREAD and LTLIBTHREAD to the linker options for use
dnl in a Makefile (LIBTHREAD for use without libtool, LTLIBTHREAD for use with
dnl libtool).
dnl Sets the variables LIBMULTITHREAD and LTLIBMULTITHREAD similarly, for
dnl programs that really need multithread functionality. The difference
dnl between LIBTHREAD and LIBMULTITHREAD is that on platforms supporting weak
dnl symbols, typically LIBTHREAD="" whereas LIBMULTITHREAD="-lpthread".
AC_DEFUN([gl_LOCK],
[
AC_REQUIRE([AC_CANONICAL_HOST])
AC_REQUIRE([AC_GNU_SOURCE]) dnl needed for pthread_rwlock_t on glibc systems
dnl Check for multithreading.
AC_ARG_ENABLE(threads,
AC_HELP_STRING([--enable-threads={posix|solaris|pth|win32}], [specify
multithreading API])
AC_HELP_STRING([--disable-threads], [build without multithread safety]),
gl_use_threads=$enableval, gl_use_threads=yes)
gl_threads_api=none
LIBTHREAD=
LTLIBTHREAD=
LIBMULTITHREAD=
LTLIBMULTITHREAD=
if test "$gl_use_threads" != no; then
dnl Check whether the compiler and linker support weak declarations.
AC_MSG_CHECKING([whether imported symbols can be declared weak])
gl_have_weak=no
AC_TRY_LINK([extern void xyzzy ();
#pragma weak xyzzy], [xyzzy();], [gl_have_weak=yes])
AC_MSG_RESULT([$gl_have_weak])
if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then
# On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that
# it groks <pthread.h>.
gl_save_CPPFLAGS="$CPPFLAGS"
CPPFLAGS="$CPPFLAGS -D_REENTRANT"
AC_CHECK_HEADER(pthread.h, gl_have_pthread_h=yes, gl_have_pthread_h=no)
CPPFLAGS="$gl_save_CPPFLAGS"
if test "$gl_have_pthread_h" = yes; then
# Other possible tests:
# -lpthreads (FSU threads, PCthreads)
# -lgthreads
case "$host_os" in
osf*)
# On OSF/1, the compiler needs the flag -pthread so that it groks
# <pthread.h>. For the linker, it is equivalent to -lpthread.
if test -n "$GCC"; then
# gcc-2.95 doesn't understand -pthread, only -D_REENTRANT.
CPPFLAGS="$CPPFLAGS -D_REENTRANT"
else
CPPFLAGS="$CPPFLAGS -pthread"
fi
;;
esac
gl_have_pthread=
AC_TRY_LINK([#include <pthread.h>],
[pthread_mutex_lock((pthread_mutex_t*)0);],
[gl_have_pthread=yes])
# Test for libpthread by looking for pthread_kill. (Not pthread_self,
# since it is defined as a macro on OSF/1.)
if test -n "$gl_have_pthread"; then
# The program links fine without libpthread. But it may actually
# need to link with libpthread in order to create multiple threads.
AC_CHECK_LIB(pthread, pthread_kill,
[LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread])
else
# Some library is needed. Try libpthread and libc_r.
AC_CHECK_LIB(pthread, pthread_kill,
[gl_have_pthread=yes
LIBTHREAD=-lpthread LTLIBTHREAD=-lpthread
LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread])
if test -z "$gl_have_pthread"; then
# For FreeBSD 4.
AC_CHECK_LIB(c_r, pthread_kill,
[gl_have_pthread=yes
LIBTHREAD=-lc_r LTLIBTHREAD=-lc_r
LIBMULTITHREAD=-lc_r LTLIBMULTITHREAD=-lc_r])
fi
fi
if test -n "$gl_have_pthread"; then
gl_threads_api=posix
AC_DEFINE([USE_POSIX_THREADS], 1,
[Define if the POSIX multithreading library can be used.])
if test -n "$LIBTHREAD" || test -n "$LTLIBTHREAD"; then
if test $gl_have_weak = yes; then
AC_DEFINE([USE_POSIX_THREADS_WEAK], 1,
[Define if references to the POSIX multithreading library
should be made weak.])
LIBTHREAD=
LTLIBTHREAD=
fi
fi
# OSF/1 4.0 and MacOS X 10.1 lack the pthread_rwlock_t type and the
# pthread_rwlock_* functions.
AC_CHECK_TYPE([pthread_rwlock_t],
[AC_DEFINE([HAVE_PTHREAD_RWLOCK], 1,
[Define if the POSIX multithreading library has read/write
locks.])],
[],
[#include <pthread.h>])
# glibc defines PTHREAD_MUTEX_RECURSIVE as enum, not as a macro.
AC_TRY_COMPILE([#include <pthread.h>],
[#if __FreeBSD__ == 4
error "No, in FreeBSD 4.0 recursive mutexes actually don't work."
#else
int x = (int)PTHREAD_MUTEX_RECURSIVE;
#endif],
[AC_DEFINE([HAVE_PTHREAD_MUTEX_RECURSIVE], 1,
[Define if the <pthread.h> defines PTHREAD_MUTEX_RECURSIVE.])])
# Some systems optimize for single-threaded programs by default, and
# need special flags to disable these optimizations.
case "$host_os" in
aix* | freebsd*) CPPFLAGS="$CPPFLAGS -D_THREAD_SAFE" ;;
solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;;
esac
fi
fi
fi
if test -z "$gl_have_pthread"; then
if test "$gl_use_threads" = yes || test "$gl_use_threads" = solaris; then
gl_have_solaristhread=
gl_save_LIBS="$LIBS"
LIBS="$LIBS -lthread"
AC_TRY_LINK([#include <thread.h>
#include <synch.h>],
[thr_self();],
[gl_have_solaristhread=yes])
LIBS="$gl_save_LIBS"
if test -n "$gl_have_solaristhread"; then
gl_threads_api=solaris
LIBTHREAD=-lthread
LTLIBTHREAD=-lthread
LIBMULTITHREAD="$LIBTHREAD"
LTLIBMULTITHREAD="$LTLIBTHREAD"
AC_DEFINE([USE_SOLARIS_THREADS], 1,
[Define if the old Solaris multithreading library can be used.])
if test $gl_have_weak = yes; then
AC_DEFINE([USE_SOLARIS_THREADS_WEAK], 1,
[Define if references to the old Solaris multithreading library
should be made weak.])
LIBTHREAD=
LTLIBTHREAD=
fi
fi
fi
fi
if test "$gl_use_threads" = pth; then
gl_save_CPPFLAGS="$CPPFLAGS"
AC_LIB_LINKFLAGS(pth)
gl_have_pth=
gl_save_LIBS="$LIBS"
LIBS="$LIBS -lpth"
AC_TRY_LINK([#include <pth.h>], [pth_self();], gl_have_pth=yes)
LIBS="$gl_save_LIBS"
if test -n "$gl_have_pth"; then
gl_threads_api=pth
LIBTHREAD="$LIBPTH"
LTLIBTHREAD="$LTLIBPTH"
LIBMULTITHREAD="$LIBTHREAD"
LTLIBMULTITHREAD="$LTLIBTHREAD"
AC_DEFINE([USE_PTH_THREADS], 1,
[Define if the GNU Pth multithreading library can be used.])
if test -n "$LIBTHREAD" || test -n "$LTLIBTHREAD"; then
if test $gl_have_weak = yes; then
AC_DEFINE([USE_PTH_THREADS_WEAK], 1,
[Define if references to the GNU Pth multithreading library
should be made weak.])
LIBTHREAD=
LTLIBTHREAD=
fi
fi
else
CPPFLAGS="$gl_save_CPPFLAGS"
fi
fi
if test -z "$gl_have_pthread"; then
if test "$gl_use_threads" = yes || test "$gl_use_threads" = win32; then
if { case "$host_os" in
mingw*) true;;
*) false;;
esac
}; then
gl_threads_api=win32
AC_DEFINE([USE_WIN32_THREADS], 1,
[Define if the Win32 multithreading API can be used.])
fi
fi
fi
fi
AC_MSG_CHECKING([for multithread API to use])
AC_MSG_RESULT([$gl_threads_api])
AC_SUBST(LIBTHREAD)
AC_SUBST(LTLIBTHREAD)
AC_SUBST(LIBMULTITHREAD)
AC_SUBST(LTLIBMULTITHREAD)
gl_PREREQ_LOCK
])
# Prerequisites of lib/lock.c.
AC_DEFUN([gl_PREREQ_LOCK], [
AC_REQUIRE([AC_C_INLINE])
])
dnl Survey of platforms:
dnl
dnl Platform Available Compiler Supports test-lock
dnl flavours option weak result
dnl --------------- --------- --------- -------- ---------
dnl Linux 2.4/glibc posix -lpthread Y OK
dnl
dnl GNU Hurd/glibc posix
dnl
dnl FreeBSD 5 posix -lc_r
dnl posix -lthr
dnl posix -lpthread
dnl
dnl FreeBSD 4.0,4.10 posix -lc_r Y OK
dnl
dnl NetBSD 1.6 --
dnl
dnl OpenBSD 3.4 posix -lpthread Y OK
dnl
dnl MacOS X 10.[123] posix -lpthread Y OK
dnl
dnl Solaris 7,8,9 posix -lpthread Y Sol 7,8: 0.0; Sol 9: OK
dnl solaris -lthread Y Sol 7,8: 0.0; Sol 9: OK
dnl
dnl HP-UX 11 posix -lpthread Y OK
dnl
dnl IRIX 6.5 posix -lpthread Y 0.5
dnl
dnl AIX 4.3,5.1 posix -lpthread N AIX 4: 0.5; AIX 5: OK
dnl
dnl OSF/1 4.0,5.1 posix -pthread (cc) Y OK
dnl -lpthread (gcc)
dnl
dnl Cygwin posix -lpthread Y OK
dnl
dnl Any of the above pth -lpth 0.0
dnl
dnl Mingw win32 N OK
dnl
dnl BeOS 5 --
dnl
dnl The test-lock result shows what happens if in test-lock.c EXPLICIT_YIELD is
dnl turned off:
dnl OK if all three tests terminate OK,
dnl 0.5 if the first test terminates OK but the second one loops endlessly,
dnl 0.0 if the first test already loops endlessly.
===============================================================================
- support for multithread-safe libraries,
Bruno Haible <=
Re: support for multithread-safe libraries, Oskar Liljeblad, 2005/07/15