/* GLIB - Library of useful routines for C programming
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* gthread.c: posix thread system implementation
* Copyright 1998 Sebastian Wilhelmi; University of Karlsruhe
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
/*
* Modified by the GLib Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GLib Team. See the ChangeLog
* files for a list of changes. These files are distributed with
* GLib at ftp://ftp.gtk.org/pub/gtk/.
*/
/* The GMutex, GCond and GPrivate implementations in this file are some
* of the lowest-level code in GLib. All other parts of GLib (messages,
* memory, slices, etc) assume that they can freely use these facilities
* without risking recursion.
*
* As such, these functions are NOT permitted to call any other part of
* GLib.
*
* The thread manipulation functions (create, exit, join, etc.) have
* more freedom -- they can do as they please.
*/
#include "config.h"
#include "gthread.h"
#include "gthreadprivate.h"
#include "gslice.h"
#include "gmessages.h"
#include "gstrfuncs.h"
#include "gmain.h"
#include "gutils.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
#include <sys/time.h>
#include <unistd.h>
#ifdef HAVE_SCHED_H
#include <sched.h>
#endif
#ifdef G_OS_WIN32
#include <windows.h>
#endif
/* clang defines __ATOMIC_SEQ_CST but doesn't support the GCC extension */
#if defined(HAVE_FUTEX) && defined(__ATOMIC_SEQ_CST) && !defined(__clang__)
#define USE_NATIVE_MUTEX
#endif
static void
g_thread_abort (gint status,
const gchar *function)
{
fprintf (stderr, "GLib (gthread-posix.c): Unexpected error from C library during '%s': %s. Aborting.\n",
function, strerror (status));
g_abort ();
}
/* {{{1 GMutex */
#if !defined(USE_NATIVE_MUTEX)
static pthread_mutex_t *
g_mutex_impl_new (void)
{
pthread_mutexattr_t *pattr = NULL;
pthread_mutex_t *mutex;
gint status;
#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
pthread_mutexattr_t attr;
#endif
mutex = malloc (sizeof (pthread_mutex_t));
if G_UNLIKELY (mutex == NULL)
g_thread_abort (errno, "malloc");
#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
pthread_mutexattr_init (&attr);
pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
pattr = &attr;
#endif
if G_UNLIKELY ((status = pthread_mutex_init (mutex, pattr)) != 0)
g_thread_abort (status, "pthread_mutex_init");
#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
pthread_mutexattr_destroy (&attr);
#endif
return mutex;
}
static void
g_mutex_impl_free (pthread_mutex_t *mutex)
{
pthread_mutex_destroy (mutex);
free (mutex);
}
static inline pthread_mutex_t *
g_mutex_get_impl (GMutex *mutex)
{
pthread_mutex_t *impl = g_atomic_pointer_get (&mutex->p);
if G_UNLIKELY (impl == NULL)
{
impl = g_mutex_impl_new ();
if (!g_atomic_pointer_compare_and_exchange (&mutex->p, NULL, impl))
g_mutex_impl_free (impl);
impl = mutex->p;
}
return impl;
}
/**
* g_mutex_init:
* @mutex: an uninitialized #GMutex
*
* Initializes a #GMutex so that it can be used.
*
* This function is useful to initialize a mutex that has been
* allocated on the stack, or as part of a larger structure.
* It is not necessary to initialize a mutex that has been
* statically allocated.
*
* |[<!-- language="C" -->
* typedef struct {
* GMutex m;
* ...
* } Blob;
*
* Blob *b;
*
* b = g_new (Blob, 1);
* g_mutex_init (&b->m);
* ]|
*
* To undo the effect of g_mutex_init() when a mutex is no longer
* needed, use g_mutex_clear().
*
* Calling g_mutex_init() on an already initialized #GMutex leads
* to undefined behaviour.
*
* Since: 2.32
*/
void
g_mutex_init (GMutex *mutex)
{
mutex->p = g_mutex_impl_new ();
}
/**
* g_mutex_clear:
* @mutex: an initialized #GMutex
*
* Frees the resources allocated to a mutex with g_mutex_init().
*
* This function should not be used with a #GMutex that has been
* statically allocated.
*
* Calling g_mutex_clear() on a locked mutex leads to undefined
* behaviour.
*
* Sine: 2.32
*/
void
g_mutex_clear (GMutex *mutex)
{
g_mutex_impl_free (mutex->p);
}
/**
* g_mutex_lock:
* @mutex: a #GMutex
*
* Locks @mutex. If @mutex is already locked by another thread, the
* current thread will block until @mutex is unlocked by the other
* thread.
*
* #GMutex is neither guaranteed to be recursive nor to be
* non-recursive. As such, calling g_mutex_lock() on a #GMutex that has
* already been locked by the same thread results in undefined behaviour
* (including but not limited to deadlocks).
*/
void
g_mutex_lock (GMutex *mutex)
{
gint status;
if G_UNLIKELY ((status = pthread_mutex_lock (g_mutex_get_impl (mutex))) != 0)
g_thread_abort (status, "pthread_mutex_lock");
}
/**
* g_mutex_unlock:
* @mutex: a #GMutex
*
* Unlocks @mutex. If another thread is blocked in a g_mutex_lock()
* call for @mutex, it will become unblocked and can lock @mutex itself.
*
* Calling g_mutex_unlock() on a mutex that is not locked by the
* current thread leads to undefined behaviour.
*/
void
g_mutex_unlock (GMutex *mutex)
{
gint status;
if G_UNLIKELY ((status = pthread_mutex_unlock (g_mutex_get_impl (mutex))) != 0)
g_thread_abort (status, "pthread_mutex_unlock");
}
/**
* g_mutex_trylock:
* @mutex: a #GMutex
*
* Tries to lock @mutex. If @mutex is already locked by another thread,
* it immediately returns %FALSE. Otherwise it locks @mutex and returns
* %TRUE.
*
* #GMutex is neither guaranteed to be recursive nor to be
* non-recursive. As such, calling g_mutex_lock() on a #GMutex that has
* already been locked by the same thread results in undefined behaviour
* (including but not limited to deadlocks or arbitrary return values).
*
* Returns: %TRUE if @mutex could be locked
*/
gboolean
g_mutex_trylock (GMutex *mutex)
{
gint status;
if G_LIKELY ((status = pthread_mutex_trylock (g_mutex_get_impl (mutex))) == 0)
return TRUE;
if G_UNLIKELY (status != EBUSY)
g_thread_abort (status, "pthread_mutex_trylock");
return FALSE;
}
#endif /* !defined(USE_NATIVE_MUTEX) */
/* {{{1 GRecMutex */
static pthread_mutex_t *
g_rec_mutex_impl_new (void)
{
pthread_mutexattr_t attr;
pthread_mutex_t *mutex;
mutex = malloc (sizeof (pthread_mutex_t));
if G_UNLIKELY (mutex == NULL)
g_thread_abort (errno, "malloc");
pthread_mutexattr_init (&attr);
pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init (mutex, &attr);
pthread_mutexattr_destroy (&attr);
return mutex;
}
static void
g_rec_mutex_impl_free (pthread_mutex_t *mutex)
{
pthread_mutex_destroy (mutex);
free (mutex);
}
static inline pthread_mutex_t *
g_rec_mutex_get_impl (GRecMutex *rec_mutex)
{
pthread_mutex_t *impl = g_atomic_pointer_get (&rec_mutex->p);
if G_UNLIKELY (impl == NULL)
{
impl = g_rec_mutex_impl_new ();
if (!g_atomic_pointer_compare_and_exchange (&rec_mutex->p, NULL, impl))
g_rec_mutex_impl_free (impl);
impl = rec_mutex->p;
}
return impl;
}
/**
* g_rec_mutex_init:
* @rec_mutex: an uninitialized #GRecMutex
*
* Initializes a #GRecMutex so that it can be used.
*
* This function is useful to initialize a recursive mutex
* that has been allocated on the stack, or as part of a larger
* structure.
*
* It is not necessary to initialise a recursive mutex that has been
* statically allocated.
*
* |[<!-- language="C" -->
* typedef struct {
* GRecMutex m;
* ...
* } Blob;
*
* Blob *b;
*
* b = g_new (Blob, 1);
* g_rec_mutex_init (&b->m);
* ]|
*
* Calling g_rec_mutex_init() on an already initialized #GRecMutex
* leads to undefined behaviour.
*
* To undo the effect of g_rec_mutex_init() when a recursive mutex
* is no longer needed, use g_rec_mutex_clear().
*
* Since: 2.32
*/
void
g_rec_mutex_init (GRecMutex *rec_mutex)
{
rec_mutex->p = g_rec_mutex_impl_new ();
}
/**
* g_rec_mutex_clear:
* @rec_mutex: an initialized #GRecMutex
*
* Frees the resources allocated to a recursive mutex with
* g_rec_mutex_init().
*
* This function should not be used with a #GRecMutex that has been
* statically allocated.
*
* Calling g_rec_mutex_clear() on a locked recursive mutex leads
* to undefined behaviour.
*
* Sine: 2.32
*/
void
g_rec_mutex_clear (GRecMutex *rec_mutex)
{
g_rec_mutex_impl_free (rec_mutex->p);
}
/**
* g_rec_mutex_lock:
* @rec_mutex: a #GRecMutex
*
* Locks @rec_mutex. If @rec_mutex is already locked by another
* thread, the current thread will block until @rec_mutex is
* unlocked by the other thread. If @rec_mutex is already locked
* by the current thread, the 'lock count' of @rec_mutex is increased.
* The mutex will only become available again when it is unlocked
* as many times as it has been locked.
*
* Since: 2.32
*/
void
g_rec_mutex_lock (GRecMutex *mutex)
{
pthread_mutex_lock (g_rec_mutex_get_impl (mutex));
}
/**
* g_rec_mutex_unlock:
* @rec_mutex: a #GRecMutex
*
* Unlocks @rec_mutex. If another thread is blocked in a
* g_rec_mutex_lock() call for @rec_mutex, it will become unblocked
* and can lock @rec_mutex itself.
*
* Calling g_rec_mutex_unlock() on a recursive mutex that is not
* locked by the current thread leads to undefined behaviour.
*
* Since: 2.32
*/
void
g_rec_mutex_unlock (GRecMutex *rec_mutex)
{
pthread_mutex_unlock (rec_mutex->p);
}
/**
* g_rec_mutex_trylock:
* @rec_mutex: a #GRecMutex
*
* Tries to lock @rec_mutex. If @rec_mutex is already locked
* by another thread, it immediately returns %FALSE. Otherwise
* it locks @rec_mutex and returns %TRUE.
*
* Returns: %TRUE if @rec_mutex could be locked
*
* Since: 2.32
*/
gboolean
g_rec_mutex_trylock (GRecMutex *rec_mutex)
{
if (pthread_mutex_trylock (g_rec_mutex_get_impl (rec_mutex)) != 0)
return FALSE;
return TRUE;
}
/* {{{1 GRWLock */
static pthread_rwlock_t *
g_rw_lock_impl_new (void)
{
pthread_rwlock_t *rwlock;
gint status;
rwlock = malloc (sizeof (pthread_rwlock_t));
if G_UNLIKELY (rwlock == NULL)
g_thread_abort (errno, "malloc");
if G_UNLIKELY ((status = pthread_rwlock_init (rwlock, NULL)) != 0)
g_thread_abort (status, "pthread_rwlock_init");
return rwlock;
}
static void
g_rw_lock_impl_free (pthread_rwlock_t *rwlock)
{
pthread_rwlock_destroy (rwlock);
free (rwlock);
}
static inline pthread_rwlock_t *
g_rw_lock_get_impl (GRWLock *lock)
{
pthread_rwlock_t *impl = g_atomic_pointer_get (&lock->p);
if G_UNLIKELY (impl == NULL)
{
impl = g_rw_lock_impl_new ();
if (!g_atomic_pointer_compare_and_exchange (&lock->p, NULL, impl))
g_rw_lock_impl_free (impl);
impl = lock->p;
}
return impl;
}
/**
* g_rw_lock_init:
* @rw_lock: an uninitialized #GRWLock
*
* Initializes a #GRWLock so that it can be used.
*
* This function is useful to initialize a lock that has been
* allocated on the stack, or as part of a larger structure. It is not
* necessary to initialise a reader-writer lock that has been statically
* allocated.
*
* |[<!-- language="C" -->
* typedef struct {
* GRWLock l;
* ...
* } Blob;
*
* Blob *b;
*
* b = g_new (Blob, 1);
* g_rw_lock_init (&b->l);
* ]|
*
* To undo the effect of g_rw_lock_init() when a lock is no longer
* needed, use g_rw_lock_clear().
*
* Calling g_rw_lock_init() on an already initialized #GRWLock leads
* to undefined behaviour.
*
* Since: 2.32
*/
void
g_rw_lock_init (GRWLock *rw_lock)
{
rw_lock->p = g_rw_lock_impl_new ();
}
/**
* g_rw_lock_clear:
* @rw_lock: an initialized #GRWLock
*
* Frees the resources allocated to a lock with g_rw_lock_init().
*
* This function should not be used with a #GRWLock that has been
* statically allocated.
*
* Calling g_rw_lock_clear() when any thread holds the lock
* leads to undefined behaviour.
*
* Sine: 2.32
*/
void
g_rw_lock_clear (GRWLock *rw_lock)
{
g_rw_lock_impl_free (rw_lock->p);
}
/**
* g_rw_lock_writer_lock:
* @rw_lock: a #GRWLock
*
* Obtain a write lock on @rw_lock. If any thread already holds
* a read or write lock on @rw_lock, the current thread will block
* until all other threads have dropped their locks on @rw_lock.
*
* Since: 2.32
*/
void
g_rw_lock_writer_lock (GRWLock *rw_lock)
{
int retval = pthread_rwlock_wrlock (g_rw_lock_get_impl (rw_lock));
if (retval != 0)
g_critical ("Failed to get RW lock %p: %s", rw_lock, g_strerror (retval));
}
/**
* g_rw_lock_writer_trylock:
* @rw_lock: a #GRWLock
*
* Tries to obtain a write lock on @rw_lock. If any other thread holds
* a read or write lock on @rw_lock, it immediately returns %FALSE.
* Otherwise it locks @rw_lock and returns %TRUE.
*
* Returns: %TRUE if @rw_lock could be locked
*
* Since: 2.32
*/
gboolean
g_rw_lock_writer_trylock (GRWLock *rw_lock)
{
if (pthread_rwlock_trywrlock (g_rw_lock_get_impl (rw_lock)) != 0)
return FALSE;
return TRUE;
}
/**
* g_rw_lock_writer_unlock:
* @rw_lock: a #GRWLock
*
* Release a write lock on @rw_lock.
*
* Calling g_rw_lock_writer_unlock() on a lock that is not held
* by the current thread leads to undefined behaviour.
*
* Since: 2.32
*/
void
g_rw_lock_writer_unlock (GRWLock *rw_lock)
{
pthread_rwlock_unlock (g_rw_lock_get_impl (rw_lock));
}
/**
* g_rw_lock_reader_lock:
* @rw_lock: a #GRWLock
*
* Obtain a read lock on @rw_lock. If another thread currently holds
* the write lock on @rw_lock or blocks waiting for it, the current
* thread will block. Read locks can be taken recursively.
*
* It is implementation-defined how many threads are allowed to
* hold read locks on the same lock simultaneously. If the limit is hit,
* or if a deadlock is detected, a critical warning will be emitted.
*
* Since: 2.32
*/
void
g_rw_lock_reader_lock (GRWLock *rw_lock)
{
int retval = pthread_rwlock_rdlock (g_rw_lock_get_impl (rw_lock));
if (retval != 0)
g_critical ("Failed to get RW lock %p: %s", rw_lock, g_strerror (retval));
}
/**
* g_rw_lock_reader_trylock:
* @rw_lock: a #GRWLock
*
* Tries to obtain a read lock on @rw_lock and returns %TRUE if
* the read lock was successfully obtained. Otherwise it
* returns %FALSE.
*
* Returns: %TRUE if @rw_lock could be locked
*
* Since: 2.32
*/
gboolean
g_rw_lock_reader_trylock (GRWLock *rw_lock)
{
if (pthread_rwlock_tryrdlock (g_rw_lock_get_impl (rw_lock)) != 0)
return FALSE;
return TRUE;
}
/**
* g_rw_lock_reader_unlock:
* @rw_lock: a #GRWLock
*
* Release a read lock on @rw_lock.
*
* Calling g_rw_lock_reader_unlock() on a lock that is not held
* by the current thread leads to undefined behaviour.
*
* Since: 2.32
*/
void
g_rw_lock_reader_unlock (GRWLock *rw_lock)
{
pthread_rwlock_unlock (g_rw_lock_get_impl (rw_lock));
}
/* {{{1 GCond */
#if !defined(USE_NATIVE_MUTEX)
static pthread_cond_t *
g_cond_impl_new (void)
{
pthread_condattr_t attr;
pthread_cond_t *cond;
gint status;
pthread_condattr_init (&attr);
#ifdef HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
#elif defined (HAVE_PTHREAD_CONDATTR_SETCLOCK) && defined (CLOCK_MONOTONIC)
if G_UNLIKELY ((status = pthread_condattr_setclock (&attr, CLOCK_MONOTONIC)) != 0)
g_thread_abort (status, "pthread_condattr_setclock");
#else
#error Cannot support GCond on your platform.
#endif
cond = malloc (sizeof (pthread_cond_t));
if G_UNLIKELY (cond == NULL)
g_thread_abort (errno, "malloc");
if G_UNLIKELY ((status = pthread_cond_init (cond, &attr)) != 0)
g_thread_abort (status, "pthread_cond_init");
pthread_condattr_destroy (&attr);
return cond;
}
static void
g_cond_impl_free (pthread_cond_t *cond)
{
pthread_cond_destroy (cond);
free (cond);
}
static inline pthread_cond_t *
g_cond_get_impl (GCond *cond)
{
pthread_cond_t *impl = g_atomic_pointer_get (&cond->p);
if G_UNLIKELY (impl == NULL)
{
impl = g_cond_impl_new ();
if (!g_atomic_pointer_compare_and_exchange (&cond->p, NULL, impl))
g_cond_impl_free (impl);
impl = cond->p;
}
return impl;
}
/**
* g_cond_init:
* @cond: an uninitialized #GCond
*
* Initialises a #GCond so that it can be used.
*
* This function is useful to initialise a #GCond that has been
* allocated as part of a larger structure. It is not necessary to
* initialise a #GCond that has been statically allocated.
*
* To undo the effect of g_cond_init() when a #GCond is no longer
* needed, use g_cond_clear().
*
* Calling g_cond_init() on an already-initialised #GCond leads
* to undefined behaviour.
*
* Since: 2.32
*/
void
g_cond_init (GCond *cond)
{
cond->p = g_cond_impl_new ();
}
/**
* g_cond_clear:
* @cond: an initialised #GCond
*
* Frees the resources allocated to a #GCond with g_cond_init().
*
* This function should not be used with a #GCond that has been
* statically allocated.
*
* Calling g_cond_clear() for a #GCond on which threads are
* blocking leads to undefined behaviour.
*
* Since: 2.32
*/
void
g_cond_clear (GCond *cond)
{
g_cond_impl_free (cond->p);
}
/**
* g_cond_wait:
* @cond: a #GCond
* @mutex: a #GMutex that is currently locked
*
* Atomically releases @mutex and waits until @cond is signalled.
* When this function returns, @mutex is locked again and owned by the
* calling thread.
*
* When using condition variables, it is possible that a spurious wakeup
* may occur (ie: g_cond_wait() returns even though g_cond_signal() was
* not called). It's also possible that a stolen wakeup may occur.
* This is when g_cond_signal() is called, but another thread acquires
* @mutex before this thread and modifies the state of the program in
* such a way that when g_cond_wait() is able to return, the expected
* condition is no longer met.
*
* For this reason, g_cond_wait() must always be used in a loop. See
* the documentation for #GCond for a complete example.
**/
void
g_cond_wait (GCond *cond,
GMutex *mutex)
{
gint status;
if G_UNLIKELY ((status = pthread_cond_wait (g_cond_get_impl (cond), g_mutex_get_impl (mutex))) != 0)
g_thread_abort (status, "pthread_cond_wait");
}
/**
* g_cond_signal:
* @cond: a #GCond
*
* If threads are waiting for @cond, at least one of them is unblocked.
* If no threads are waiting for @cond, this function has no effect.
* It is good practice to hold the same lock as the waiting thread
* while calling this function, though not required.
*/
void
g_cond_signal (GCond *cond)
{
gint status;
if G_UNLIKELY ((status = pthread_cond_signal (g_cond_get_impl (cond))) != 0)
g_thread_abort (status, "pthread_cond_signal");
}
/**
* g_cond_broadcast:
* @cond: a #GCond
*
* If threads are waiting for @cond, all of them are unblocked.
* If no threads are waiting for @cond, this function has no effect.
* It is good practice to lock the same mutex as the waiting threads
* while calling this function, though not required.
*/
void
g_cond_broadcast (GCond *cond)
{
gint status;
if G_UNLIKELY ((status = pthread_cond_broadcast (g_cond_get_impl (cond))) != 0)
g_thread_abort (status, "pthread_cond_broadcast");
}
/**
* g_cond_wait_until:
* @cond: a #GCond
* @mutex: a #GMutex that is currently locked
* @end_time: the monotonic time to wait until
*
* Waits until either @cond is signalled or @end_time has passed.
*
* As with g_cond_wait() it is possible that a spurious or stolen wakeup
* could occur. For that reason, waiting on a condition variable should
* always be in a loop, based on an explicitly-checked predicate.
*
* %TRUE is returned if the condition variable was signalled (or in the
* case of a spurious wakeup). %FALSE is returned if @end_time has
* passed.
*
* The following code shows how to correctly perform a timed wait on a
* condition variable (extending the example presented in the
* documentation for #GCond):
*
* |[<!-- language="C" -->
* gpointer
* pop_data_timed (void)
* {
* gint64 end_time;
* gpointer data;
*
* g_mutex_lock (&data_mutex);
*
* end_time = g_get_monotonic_time () + 5 * G_TIME_SPAN_SECOND;
* while (!current_data)
* if (!g_cond_wait_until (&data_cond, &data_mutex, end_time))
* {
* // timeout has passed.
* g_mutex_unlock (&data_mutex);
* return NULL;
* }
*
* // there is data for us
* data = current_data;
* current_data = NULL;
*
* g_mutex_unlock (&data_mutex);
*
* return data;
* }
* ]|
*
* Notice that the end time is calculated once, before entering the
* loop and reused. This is the motivation behind the use of absolute
* time on this API -- if a relative time of 5 seconds were passed
* directly to the call and a spurious wakeup occurred, the program would
* have to start over waiting again (which would lead to a total wait
* time of more than 5 seconds).
*
* Returns: %TRUE on a signal, %FALSE on a timeout
* Since: 2.32
**/
gboolean
g_cond_wait_until (GCond *cond,
GMutex *mutex,
gint64 end_time)
{
struct timespec ts;
gint status;
#ifdef HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE_NP
/* end_time is given relative to the monotonic clock as returned by
* g_get_monotonic_time().
*
* Since this pthreads wants the relative time, convert it back again.
*/
{
gint64 now = g_get_monotonic_time ();
gint64 relative;
if (end_time <= now)
return FALSE;
relative = end_time - now;
ts.tv_sec = relative / 1000000;
ts.tv_nsec = (relative % 1000000) * 1000;
if ((status = pthread_cond_timedwait_relative_np (g_cond_get_impl (cond), g_mutex_get_impl (mutex), &ts)) == 0)
return TRUE;
}
#elif defined (HAVE_PTHREAD_CONDATTR_SETCLOCK) && defined (CLOCK_MONOTONIC)
/* This is the exact check we used during init to set the clock to
* monotonic, so if we're in this branch, timedwait() will already be
* expecting a monotonic clock.
*/
{
ts.tv_sec = end_time / 1000000;
ts.tv_nsec = (end_time % 1000000) * 1000;
if ((status = pthread_cond_timedwait (g_cond_get_impl (cond), g_mutex_get_impl (mutex), &ts)) == 0)
return TRUE;
}
#else
#error Cannot support GCond on your platform.
#endif
if G_UNLIKELY (status != ETIMEDOUT)
g_thread_abort (status, "pthread_cond_timedwait");
return FALSE;
}
#endif /* defined(USE_NATIVE_MUTEX) */
/* {{{1 GPrivate */
/**
* GPrivate:
*
* The #GPrivate struct is an opaque data structure to represent a
* thread-local data key. It is approximately equivalent to the
* pthread_setspecific()/pthread_getspecific() APIs on POSIX and to
* TlsSetValue()/TlsGetValue() on Windows.
*
* If you don't already know why you might want this functionality,
* then you probably don't need it.
*
* #GPrivate is a very limited resource (as far as 128 per program,
* shared between all libraries). It is also not possible to destroy a
* #GPrivate after it has been used. As such, it is only ever acceptable
* to use #GPrivate in static scope, and even then sparingly so.
*
* See G_PRIVATE_INIT() for a couple of examples.
*
* The #GPrivate structure should be considered opaque. It should only
* be accessed via the g_private_ functions.
*/
/**
* G_PRIVATE_INIT:
* @notify: a #GDestroyNotify
*
* A macro to assist with the static initialisation of a #GPrivate.
*
* This macro is useful for the case that a #GDestroyNotify function
* should be associated with the key. This is needed when the key will be
* used to point at memory that should be deallocated when the thread
* exits.
*
* Additionally, the #GDestroyNotify will also be called on the previous
* value stored in the key when g_private_replace() is used.
*
* If no #GDestroyNotify is needed, then use of this macro is not
* required -- if the #GPrivate is declared in static scope then it will
* be properly initialised by default (ie: to all zeros). See the
* examples below.
*
* |[<!-- language="C" -->
* static GPrivate name_key = G_PRIVATE_INIT (g_free);
*
* // return value should not be freed
* const gchar *
* get_local_name (void)
* {
* return g_private_get (&name_key);
* }
*
* void
* set_local_name (const gchar *name)
* {
* g_private_replace (&name_key, g_strdup (name));
* }
*
*
* static GPrivate count_key; // no free function
*
* gint
* get_local_count (void)
* {
* return GPOINTER_TO_INT (g_private_get (&count_key));
* }
*
* void
* set_local_count (gint count)
* {
* g_private_set (&count_key, GINT_TO_POINTER (count));
* }
* ]|
*
* Since: 2.32
**/
static pthread_key_t *
g_private_impl_new (GDestroyNotify notify)
{
pthread_key_t *key;
gint status;
key = malloc (sizeof (pthread_key_t));
if G_UNLIKELY (key == NULL)
g_thread_abort (errno, "malloc");
status = pthread_key_create (key, notify);
if G_UNLIKELY (status != 0)
g_thread_abort (status, "pthread_key_create");
return key;
}
static void
g_private_impl_free (pthread_key_t *key)
{
gint status;
status = pthread_key_delete (*key);
if G_UNLIKELY (status != 0)
g_thread_abort (status, "pthread_key_delete");
free (key);
}
static inline pthread_key_t *
g_private_get_impl (GPrivate *key)
{
pthread_key_t *impl = g_atomic_pointer_get (&key->p);
if G_UNLIKELY (impl == NULL)
{
impl = g_private_impl_new (key->notify);
if (!g_atomic_pointer_compare_and_exchange (&key->p, NULL, impl))
{
g_private_impl_free (impl);
impl = key->p;
}
}
return impl;
}
/**
* g_private_get:
* @key: a #GPrivate
*
* Returns the current value of the thread local variable @key.
*
* If the value has not yet been set in this thread, %NULL is returned.
* Values are never copied between threads (when a new thread is
* created, for example).
*
* Returns: the thread-local value
*/
gpointer
g_private_get (GPrivate *key)
{
/* quote POSIX: No errors are returned from pthread_getspecific(). */
return pthread_getspecific (*g_private_get_impl (key));
}
/**
* g_private_set:
* @key: a #GPrivate
* @value: the new value
*
* Sets the thread local variable @key to have the value @value in the
* current thread.
*
* This function differs from g_private_replace() in the following way:
* the #GDestroyNotify for @key is not called on the old value.
*/
void
g_private_set (GPrivate *key,
gpointer value)
{
gint status;
if G_UNLIKELY ((status = pthread_setspecific (*g_private_get_impl (key), value)) != 0)
g_thread_abort (status, "pthread_setspecific");
}
/**
* g_private_replace:
* @key: a #GPrivate
* @value: the new value
*
* Sets the thread local variable @key to have the value @value in the
* current thread.
*
* This function differs from g_private_set() in the following way: if
* the previous value was non-%NULL then the #GDestroyNotify handler for
* @key is run on it.
*
* Since: 2.32
**/
void
g_private_replace (GPrivate *key,
gpointer value)
{
pthread_key_t *impl = g_private_get_impl (key);
gpointer old;
gint status;
old = pthread_getspecific (*impl);
if (old && key->notify)
key->notify (old);
if G_UNLIKELY ((status = pthread_setspecific (*impl, value)) != 0)
g_thread_abort (status, "pthread_setspecific");
}
/* {{{1 GThread */
#define posix_check_err(err, name) G_STMT_START{ \
int error = (err); \
if (error) \
g_error ("file %s: line %d (%s): error '%s' during '%s'", \
__FILE__, __LINE__, G_STRFUNC, \
g_strerror (error), name); \
}G_STMT_END
#define posix_check_cmd(cmd) posix_check_err (cmd, #cmd)
typedef struct
{
GRealThread thread;
pthread_t system_thread;
gboolean joined;
GMutex lock;
} GThreadPosix;
void
g_system_thread_free (GRealThread *thread)
{
GThreadPosix *pt = (GThreadPosix *) thread;
if (!pt->joined)
pthread_detach (pt->system_thread);
g_mutex_clear (&pt->lock);
g_slice_free (GThreadPosix, pt);
}
GRealThread *
g_system_thread_new (GThreadFunc thread_func,
gulong stack_size,
GError **error)
{
GThreadPosix *thread;
pthread_attr_t attr;
gint ret;
thread = g_slice_new0 (GThreadPosix);
posix_check_cmd (pthread_attr_init (&attr));
#ifdef HAVE_PTHREAD_ATTR_SETSTACKSIZE
if (stack_size)
{
#ifdef _SC_THREAD_STACK_MIN
long min_stack_size = sysconf (_SC_THREAD_STACK_MIN);
if (min_stack_size >= 0)
stack_size = MAX (min_stack_size, stack_size);
#endif /* _SC_THREAD_STACK_MIN */
/* No error check here, because some systems can't do it and
* we simply don't want threads to fail because of that. */
pthread_attr_setstacksize (&attr, stack_size);
}
#endif /* HAVE_PTHREAD_ATTR_SETSTACKSIZE */
ret = pthread_create (&thread->system_thread, &attr, (void* (*)(void*))thread_func, thread);
posix_check_cmd (pthread_attr_destroy (&attr));
if (ret == EAGAIN)
{
g_set_error (error, G_THREAD_ERROR, G_THREAD_ERROR_AGAIN,
"Error creating thread: %s", g_strerror (ret));
g_slice_free (GThreadPosix, thread);
return NULL;
}
posix_check_err (ret, "pthread_create");
g_mutex_init (&thread->lock);
return (GRealThread *) thread;
}
/**
* g_thread_yield:
*
* Causes the calling thread to voluntarily relinquish the CPU, so
* that other threads can run.
*
* This function is often used as a method to make busy wait less evil.
*/
void
g_thread_yield (void)
{
sched_yield ();
}
void
g_system_thread_wait (GRealThread *thread)
{
GThreadPosix *pt = (GThreadPosix *) thread;
g_mutex_lock (&pt->lock);
if (!pt->joined)
{
posix_check_cmd (pthread_join (pt->system_thread, NULL));
pt->joined = TRUE;
}
g_mutex_unlock (&pt->lock);
}
void
g_system_thread_exit (void)
{
pthread_exit (NULL);
}
void
g_system_thread_set_name (const gchar *name)
{
#if defined(HAVE_PTHREAD_SETNAME_NP_WITH_TID)
pthread_setname_np (pthread_self(), name); /* on Linux and Solaris */
#elif defined(HAVE_PTHREAD_SETNAME_NP_WITHOUT_TID)
pthread_setname_np (name); /* on OS X and iOS */
#endif
}
/* {{{1 GMutex and GCond futex implementation */
#if defined(USE_NATIVE_MUTEX)
#include <linux/futex.h>
#include <sys/syscall.h>
#ifndef FUTEX_WAIT_PRIVATE
#define FUTEX_WAIT_PRIVATE FUTEX_WAIT
#define FUTEX_WAKE_PRIVATE FUTEX_WAKE
#endif
/* We should expand the set of operations available in gatomic once we
* have better C11 support in GCC in common distributions (ie: 4.9).
*
* Before then, let's define a couple of useful things for our own
* purposes...
*/
#define exchange_acquire(ptr, new) \
__atomic_exchange_4((ptr), (new), __ATOMIC_ACQUIRE)
#define compare_exchange_acquire(ptr, old, new) \
__atomic_compare_exchange_4((ptr), (old), (new), 0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)
#define exchange_release(ptr, new) \
__atomic_exchange_4((ptr), (new), __ATOMIC_RELEASE)
#define store_release(ptr, new) \
__atomic_store_4((ptr), (new), __ATOMIC_RELEASE)
/* Our strategy for the mutex is pretty simple:
*
* 0: not in use
*
* 1: acquired by one thread only, no contention
*
* > 1: contended
*
*
* As such, attempting to acquire the lock should involve an increment.
* If we find that the previous value was 0 then we can return
* immediately.
*
* On unlock, we always store 0 to indicate that the lock is available.
* If the value there was 1 before then we didn't have contention and
* can return immediately. If the value was something other than 1 then
* we have the contended case and need to wake a waiter.
*
* If it was not 0 then there is another thread holding it and we must
* wait. We must always ensure that we mark a value >1 while we are
* waiting in order to instruct the holder to do a wake operation on
* unlock.
*/
void
g_mutex_init (GMutex *mutex)
{
mutex->i[0] = 0;
}
void
g_mutex_clear (GMutex *mutex)
{
if G_UNLIKELY (mutex->i[0] != 0)
{
fprintf (stderr, "g_mutex_clear() called on uninitialised or locked mutex\n");
g_abort ();
}
}
static void __attribute__((noinline))
g_mutex_lock_slowpath (GMutex *mutex)
{
/* Set to 2 to indicate contention. If it was zero before then we
* just acquired the lock.
*
* Otherwise, sleep for as long as the 2 remains...
*/
while (exchange_acquire (&mutex->i[0], 2) != 0)
syscall (__NR_futex, &mutex->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) 2, NULL);
}
static void __attribute__((noinline))
g_mutex_unlock_slowpath (GMutex *mutex,
guint prev)
{
/* We seem to get better code for the uncontended case by splitting
* this out...
*/
if G_UNLIKELY (prev == 0)
{
fprintf (stderr, "Attempt to unlock mutex that was not locked\n");
g_abort ();
}
syscall (__NR_futex, &mutex->i[0], (gsize) FUTEX_WAKE_PRIVATE, (gsize) 1, NULL);
}
void
g_mutex_lock (GMutex *mutex)
{
/* 0 -> 1 and we're done. Anything else, and we need to wait... */
if G_UNLIKELY (g_atomic_int_add (&mutex->i[0], 1) != 0)
g_mutex_lock_slowpath (mutex);
}
void
g_mutex_unlock (GMutex *mutex)
{
guint prev;
prev = exchange_release (&mutex->i[0], 0);
/* 1-> 0 and we're done. Anything else and we need to signal... */
if G_UNLIKELY (prev != 1)
g_mutex_unlock_slowpath (mutex, prev);
}
gboolean
g_mutex_trylock (GMutex *mutex)
{
guint zero = 0;
/* We don't want to touch the value at all unless we can move it from
* exactly 0 to 1.
*/
return compare_exchange_acquire (&mutex->i[0], &zero, 1);
}
/* Condition variables are implemented in a rather simple way as well.
* In many ways, futex() as an abstraction is even more ideally suited
* to condition variables than it is to mutexes.
*
* We store a generation counter. We sample it with the lock held and
* unlock before sleeping on the futex.
*
* Signalling simply involves increasing the counter and making the
* appropriate futex call.
*
* The only thing that is the slightest bit complicated is timed waits
* because we must convert our absolute time to relative.
*/
void
g_cond_init (GCond *cond)
{
cond->i[0] = 0;
}
void
g_cond_clear (GCond *cond)
{
}
void
g_cond_wait (GCond *cond,
GMutex *mutex)
{
guint sampled = g_atomic_int_get (&cond->i[0]);
g_mutex_unlock (mutex);
syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) sampled, NULL);
g_mutex_lock (mutex);
}
void
g_cond_signal (GCond *cond)
{
g_atomic_int_inc (&cond->i[0]);
syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAKE_PRIVATE, (gsize) 1, NULL);
}
void
g_cond_broadcast (GCond *cond)
{
g_atomic_int_inc (&cond->i[0]);
syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAKE_PRIVATE, (gsize) INT_MAX, NULL);
}
gboolean
g_cond_wait_until (GCond *cond,
GMutex *mutex,
gint64 end_time)
{
struct timespec now;
struct timespec span;
guint sampled;
int res;
if (end_time < 0)
return FALSE;
clock_gettime (CLOCK_MONOTONIC, &now);
span.tv_sec = (end_time / 1000000) - now.tv_sec;
span.tv_nsec = ((end_time % 1000000) * 1000) - now.tv_nsec;
if (span.tv_nsec < 0)
{
span.tv_nsec += 1000000000;
span.tv_sec--;
}
if (span.tv_sec < 0)
return FALSE;
sampled = cond->i[0];
g_mutex_unlock (mutex);
res = syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) sampled, &span);
g_mutex_lock (mutex);
return (res < 0 && errno == ETIMEDOUT) ? FALSE : TRUE;
}
#endif
/* {{{1 Epilogue */
/* vim:set foldmethod=marker: */