| /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */ |
| /* dbus-sysdeps-pthread.c Implements threads using pthreads (internal to libdbus) |
| * |
| * Copyright (C) 2002, 2003, 2006 Red Hat, Inc. |
| * |
| * Licensed under the Academic Free License version 2.1 |
| * |
| * This program 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 of the License, 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 General Public License for more details. |
| * |
| * You should have received a copy of the GNU 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 |
| * |
| */ |
| |
| #include <config.h> |
| #include "dbus-internals.h" |
| #include "dbus-sysdeps.h" |
| #include "dbus-threads.h" |
| |
| #include <sys/time.h> |
| #include <pthread.h> |
| #include <string.h> |
| |
| #ifdef HAVE_ERRNO_H |
| #include <errno.h> |
| #endif |
| |
| #include <config.h> |
| |
| /* Whether we have a "monotonic" clock; i.e. a clock not affected by |
| * changes in system time. |
| * This is initialized once in check_monotonic_clock below. |
| * https://bugs.freedesktop.org/show_bug.cgi?id=18121 |
| */ |
| static dbus_bool_t have_monotonic_clock = 0; |
| |
| typedef struct { |
| pthread_mutex_t lock; /**< lock protecting count field */ |
| volatile int count; /**< count of how many times lock holder has recursively locked */ |
| volatile pthread_t holder; /**< holder of the lock if count >0, |
| valid but arbitrary thread if count |
| has ever been >0, uninitialized memory |
| if count has never been >0 */ |
| } DBusMutexPThread; |
| |
| typedef struct { |
| pthread_cond_t cond; /**< the condition */ |
| } DBusCondVarPThread; |
| |
| #define DBUS_MUTEX(m) ((DBusMutex*) m) |
| #define DBUS_MUTEX_PTHREAD(m) ((DBusMutexPThread*) m) |
| |
| #define DBUS_COND_VAR(c) ((DBusCondVar*) c) |
| #define DBUS_COND_VAR_PTHREAD(c) ((DBusCondVarPThread*) c) |
| |
| |
| #ifdef DBUS_DISABLE_ASSERT |
| /* (tmp != 0) is a no-op usage to silence compiler */ |
| #define PTHREAD_CHECK(func_name, result_or_call) \ |
| do { int tmp = (result_or_call); if (tmp != 0) {;} } while (0) |
| #else |
| #define PTHREAD_CHECK(func_name, result_or_call) do { \ |
| int tmp = (result_or_call); \ |
| if (tmp != 0) { \ |
| _dbus_warn_check_failed ("pthread function %s failed with %d %s in %s\n", \ |
| func_name, tmp, strerror(tmp), _DBUS_FUNCTION_NAME); \ |
| } \ |
| } while (0) |
| #endif /* !DBUS_DISABLE_ASSERT */ |
| |
| static DBusMutex* |
| _dbus_pthread_mutex_new (void) |
| { |
| DBusMutexPThread *pmutex; |
| int result; |
| |
| pmutex = dbus_new (DBusMutexPThread, 1); |
| if (pmutex == NULL) |
| return NULL; |
| |
| result = pthread_mutex_init (&pmutex->lock, NULL); |
| |
| if (result == ENOMEM || result == EAGAIN) |
| { |
| dbus_free (pmutex); |
| return NULL; |
| } |
| else |
| { |
| PTHREAD_CHECK ("pthread_mutex_init", result); |
| } |
| |
| /* Only written */ |
| pmutex->count = 0; |
| |
| /* There's no portable way to have a "null" pthread afaik so we |
| * can't set pmutex->holder to anything sensible. We only access it |
| * once the lock is held (which means we've set it). |
| */ |
| |
| return DBUS_MUTEX (pmutex); |
| } |
| |
| static void |
| _dbus_pthread_mutex_free (DBusMutex *mutex) |
| { |
| DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex); |
| |
| _dbus_assert (pmutex->count == 0); |
| |
| PTHREAD_CHECK ("pthread_mutex_destroy", pthread_mutex_destroy (&pmutex->lock)); |
| |
| dbus_free (pmutex); |
| } |
| |
| static void |
| _dbus_pthread_mutex_lock (DBusMutex *mutex) |
| { |
| DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex); |
| pthread_t self = pthread_self (); |
| |
| /* If the count is > 0 then someone had the lock, maybe us. If it is |
| * 0, then it might immediately change right after we read it, |
| * but it will be changed by another thread; i.e. if we read 0, |
| * we assume that this thread doesn't have the lock. |
| * |
| * Not 100% sure this is safe, but ... seems like it should be. |
| */ |
| if (pmutex->count == 0) |
| { |
| /* We know we don't have the lock; someone may have the lock. */ |
| |
| PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock)); |
| |
| /* We now have the lock. Count must be 0 since it must be 0 when |
| * the lock is released by another thread, and we just now got |
| * the lock. |
| */ |
| _dbus_assert (pmutex->count == 0); |
| |
| pmutex->holder = self; |
| pmutex->count = 1; |
| } |
| else |
| { |
| /* We know someone had the lock, possibly us. Thus |
| * pmutex->holder is not pointing to junk, though it may not be |
| * the lock holder anymore if the lock holder is not us. If the |
| * lock holder is us, then we definitely have the lock. |
| */ |
| |
| if (pthread_equal (pmutex->holder, self)) |
| { |
| /* We already have the lock. */ |
| _dbus_assert (pmutex->count > 0); |
| } |
| else |
| { |
| /* Wait for the lock */ |
| PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock)); |
| pmutex->holder = self; |
| _dbus_assert (pmutex->count == 0); |
| } |
| |
| pmutex->count += 1; |
| } |
| } |
| |
| static void |
| _dbus_pthread_mutex_unlock (DBusMutex *mutex) |
| { |
| DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex); |
| |
| _dbus_assert (pmutex->count > 0); |
| |
| pmutex->count -= 1; |
| |
| if (pmutex->count == 0) |
| PTHREAD_CHECK ("pthread_mutex_unlock", pthread_mutex_unlock (&pmutex->lock)); |
| |
| /* We leave pmutex->holder set to ourselves, its content is undefined if count is 0 */ |
| } |
| |
| static DBusCondVar * |
| _dbus_pthread_condvar_new (void) |
| { |
| DBusCondVarPThread *pcond; |
| pthread_condattr_t attr; |
| int result; |
| |
| pcond = dbus_new (DBusCondVarPThread, 1); |
| if (pcond == NULL) |
| return NULL; |
| |
| pthread_condattr_init (&attr); |
| #ifdef HAVE_MONOTONIC_CLOCK |
| if (have_monotonic_clock) |
| pthread_condattr_setclock (&attr, CLOCK_MONOTONIC); |
| #endif |
| |
| result = pthread_cond_init (&pcond->cond, &attr); |
| pthread_condattr_destroy (&attr); |
| |
| if (result == EAGAIN || result == ENOMEM) |
| { |
| dbus_free (pcond); |
| return NULL; |
| } |
| else |
| { |
| PTHREAD_CHECK ("pthread_cond_init", result); |
| } |
| |
| return DBUS_COND_VAR (pcond); |
| } |
| |
| static void |
| _dbus_pthread_condvar_free (DBusCondVar *cond) |
| { |
| DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond); |
| |
| PTHREAD_CHECK ("pthread_cond_destroy", pthread_cond_destroy (&pcond->cond)); |
| |
| dbus_free (pcond); |
| } |
| |
| static void |
| _dbus_pthread_condvar_wait (DBusCondVar *cond, |
| DBusMutex *mutex) |
| { |
| DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex); |
| DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond); |
| int old_count; |
| |
| _dbus_assert (pmutex->count > 0); |
| _dbus_assert (pthread_equal (pmutex->holder, pthread_self ())); |
| |
| old_count = pmutex->count; |
| pmutex->count = 0; /* allow other threads to lock */ |
| PTHREAD_CHECK ("pthread_cond_wait", pthread_cond_wait (&pcond->cond, &pmutex->lock)); |
| _dbus_assert (pmutex->count == 0); |
| pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */ |
| |
| /* The order of this line and the above line is important. |
| * See the comments below at the end of _dbus_pthread_condvar_wait_timeout |
| */ |
| pmutex->count = old_count; |
| } |
| |
| static dbus_bool_t |
| _dbus_pthread_condvar_wait_timeout (DBusCondVar *cond, |
| DBusMutex *mutex, |
| int timeout_milliseconds) |
| { |
| DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex); |
| DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond); |
| struct timeval time_now; |
| struct timespec end_time; |
| int result; |
| int old_count; |
| |
| _dbus_assert (pmutex->count > 0); |
| _dbus_assert (pthread_equal (pmutex->holder, pthread_self ())); |
| |
| #ifdef HAVE_MONOTONIC_CLOCK |
| if (have_monotonic_clock) |
| { |
| struct timespec monotonic_timer; |
| clock_gettime (CLOCK_MONOTONIC,&monotonic_timer); |
| time_now.tv_sec = monotonic_timer.tv_sec; |
| time_now.tv_usec = monotonic_timer.tv_nsec / 1000; |
| } |
| else |
| /* This else falls through to gettimeofday */ |
| #endif |
| gettimeofday (&time_now, NULL); |
| |
| end_time.tv_sec = time_now.tv_sec + timeout_milliseconds / 1000; |
| end_time.tv_nsec = (time_now.tv_usec + (timeout_milliseconds % 1000) * 1000) * 1000; |
| if (end_time.tv_nsec > 1000*1000*1000) |
| { |
| end_time.tv_sec += 1; |
| end_time.tv_nsec -= 1000*1000*1000; |
| } |
| |
| old_count = pmutex->count; |
| pmutex->count = 0; |
| result = pthread_cond_timedwait (&pcond->cond, &pmutex->lock, &end_time); |
| |
| if (result != ETIMEDOUT) |
| { |
| PTHREAD_CHECK ("pthread_cond_timedwait", result); |
| } |
| |
| _dbus_assert (pmutex->count == 0); |
| pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */ |
| |
| /* restore to old count after setting the owner back to self, |
| * If reversing this line with above line, the previous owner thread could |
| * get into the mutex without proper locking by passing the lock owner check. |
| */ |
| pmutex->count = old_count; |
| |
| /* return true if we did not time out */ |
| return result != ETIMEDOUT; |
| } |
| |
| static void |
| _dbus_pthread_condvar_wake_one (DBusCondVar *cond) |
| { |
| DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond); |
| |
| PTHREAD_CHECK ("pthread_cond_signal", pthread_cond_signal (&pcond->cond)); |
| } |
| |
| static void |
| _dbus_pthread_condvar_wake_all (DBusCondVar *cond) |
| { |
| DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond); |
| |
| PTHREAD_CHECK ("pthread_cond_broadcast", pthread_cond_broadcast (&pcond->cond)); |
| } |
| |
| static const DBusThreadFunctions pthread_functions = |
| { |
| DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK | |
| DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK | |
| DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK | |
| DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK | |
| DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK | |
| DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK | |
| DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK | |
| DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK | |
| DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK| |
| DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK, |
| NULL, NULL, NULL, NULL, |
| _dbus_pthread_condvar_new, |
| _dbus_pthread_condvar_free, |
| _dbus_pthread_condvar_wait, |
| _dbus_pthread_condvar_wait_timeout, |
| _dbus_pthread_condvar_wake_one, |
| _dbus_pthread_condvar_wake_all, |
| _dbus_pthread_mutex_new, |
| _dbus_pthread_mutex_free, |
| _dbus_pthread_mutex_lock, |
| _dbus_pthread_mutex_unlock |
| }; |
| |
| static void |
| check_monotonic_clock (void) |
| { |
| #ifdef HAVE_MONOTONIC_CLOCK |
| struct timespec dummy; |
| if (clock_getres (CLOCK_MONOTONIC, &dummy) == 0) |
| have_monotonic_clock = TRUE; |
| #endif |
| } |
| |
| dbus_bool_t |
| _dbus_threads_init_platform_specific (void) |
| { |
| check_monotonic_clock (); |
| return dbus_threads_init (&pthread_functions); |
| } |