lock.h

asterisk 是一个很有知名度开源软件

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <[e-mail]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 * \brief Asterisk locking-related definitions:
 * - ast_mutext_t, ast_rwlock_t and related functions;
 * - atomic arithmetic instructions;
 * - wrappers for channel locking.
 *
 * - See \ref LockDef
 */

/*! \page LockDef Asterisk thread locking models
 *
 * This file provides different implementation of the functions,
 * depending on the platform, the use of DEBUG_THREADS, and the way
 * module-level mutexes are initialized.
 *
 *  - \b static: the mutex is assigned the value AST_MUTEX_INIT_VALUE
 *        this is done at compile time, and is the way used on Linux.
 *        This method is not applicable to all platforms e.g. when the
 *        initialization needs that some code is run.
 *
 *  - \b through constructors: for each mutex, a constructor function is
 *        defined, which then runs when the program (or the module)
 *        starts. The problem with this approach is that there is a
 *        lot of code duplication (a new block of code is created for
 *        each mutex). Also, it does not prevent a user from declaring
 *        a global mutex without going through the wrapper macros,
 *        so sane programming practices are still required.
 */

#ifndef _ASTERISK_LOCK_H
#define _ASTERISK_LOCK_H

#include <pthread.h>
#include <sys/param.h>

#include "asterisk/logger.h"

/* internal macro to profile mutexes. Only computes the delay on
 * non-blocking calls.
 */
#ifndef	HAVE_MTX_PROFILE
#define	__MTX_PROF(a)	return pthread_mutex_lock((a))
#else
#define	__MTX_PROF(a)	do {			\
	int i;					\
	/* profile only non-blocking events */	\
	ast_mark(mtx_prof, 1);			\
	i = pthread_mutex_trylock((a));		\
	ast_mark(mtx_prof, 0);			\
	if (!i)					\
		return i;			\
	else					\
		return pthread_mutex_lock((a)); \
	} while (0)
#endif	/* HAVE_MTX_PROFILE */

#define AST_PTHREADT_NULL (pthread_t) -1
#define AST_PTHREADT_STOP (pthread_t) -2

#if defined(SOLARIS) || defined(BSD)
#define AST_MUTEX_INIT_W_CONSTRUCTORS
#endif /* SOLARIS || BSD */

/* Asterisk REQUIRES recursive (not error checking) mutexes
   and will not run without them. */
#if defined(HAVE_PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP) && defined(HAVE_PTHREAD_MUTEX_RECURSIVE_NP)
#define PTHREAD_MUTEX_INIT_VALUE	PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
#define AST_MUTEX_KIND			PTHREAD_MUTEX_RECURSIVE_NP
#else
#define PTHREAD_MUTEX_INIT_VALUE	PTHREAD_MUTEX_INITIALIZER
#define AST_MUTEX_KIND			PTHREAD_MUTEX_RECURSIVE
#endif /* PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP */

/*
 * Definition of ast_mutex_t, ast_cont_d and related functions with/without debugging
 * (search for DEBUG_THREADS to find the start/end of the sections).
 *
 * The non-debug code contains just wrappers for the corresponding pthread functions.
 * The debug code tracks usage and tries to identify deadlock situations.
 */
#ifdef DEBUG_THREADS

#define __ast_mutex_logger(...)  do { if (canlog) ast_log(LOG_ERROR, __VA_ARGS__); else fprintf(stderr, __VA_ARGS__); } while (0)

#ifdef THREAD_CRASH
#define DO_THREAD_CRASH do { *((int *)(0)) = 1; } while(0)
#else
#define DO_THREAD_CRASH do { } while (0)
#endif

#include <errno.h>

#define AST_MUTEX_INIT_VALUE { PTHREAD_MUTEX_INIT_VALUE, 1, { NULL }, { 0 }, 0, { NULL }, { 0 }, PTHREAD_MUTEX_INIT_VALUE }
#define AST_MUTEX_INIT_VALUE_NOTRACKING \
                             { PTHREAD_MUTEX_INIT_VALUE, 0, { NULL }, { 0 }, 0, { NULL }, { 0 }, PTHREAD_MUTEX_INIT_VALUE }

#define AST_MAX_REENTRANCY 10

struct ast_channel;

struct ast_mutex_info {
	pthread_mutex_t mutex;
	/*! Track which thread holds this lock */
	unsigned int track:1;
	const char *file[AST_MAX_REENTRANCY];
	int lineno[AST_MAX_REENTRANCY];
	int reentrancy;
	const char *func[AST_MAX_REENTRANCY];
	pthread_t thread[AST_MAX_REENTRANCY];
	pthread_mutex_t reentr_mutex;
};

typedef struct ast_mutex_info ast_mutex_t;

typedef pthread_cond_t ast_cond_t;

static pthread_mutex_t empty_mutex;

enum ast_lock_type {
	AST_MUTEX,
	AST_RDLOCK,
	AST_WRLOCK,
};

/*!
 * \brief Store lock info for the current thread
 *
 * This function gets called in ast_mutex_lock() and ast_mutex_trylock() so
 * that information about this lock can be stored in this thread's
 * lock info struct.  The lock is marked as pending as the thread is waiting
 * on the lock.  ast_mark_lock_acquired() will mark it as held by this thread.
 */
#if !defined(LOW_MEMORY)
void ast_store_lock_info(enum ast_lock_type type, const char *filename,
	int line_num, const char *func, const char *lock_name, void *lock_addr);
#else
#define ast_store_lock_info(I,DONT,CARE,ABOUT,THE,PARAMETERS)
#endif


/*!
 * \brief Mark the last lock as acquired
 */
#if !defined(LOW_MEMORY)
void ast_mark_lock_acquired(void *lock_addr);
#else
#define ast_mark_lock_acquired(ignore)
#endif

/*!
 * \brief Mark the last lock as failed (trylock)
 */
#if !defined(LOW_MEMORY)
void ast_mark_lock_failed(void *lock_addr);
#else
#define ast_mark_lock_failed(ignore)
#endif

/*!
 * \brief remove lock info for the current thread
 *
 * this gets called by ast_mutex_unlock so that information on the lock can
 * be removed from the current thread's lock info struct.
 */
#if !defined(LOW_MEMORY)
void ast_remove_lock_info(void *lock_addr);
#else
#define ast_remove_lock_info(ignore)
#endif

/*!
 * \brief retrieve lock info for the specified mutex
 *
 * this gets called during deadlock avoidance, so that the information may
 * be preserved as to what location originally acquired the lock.
 */
#if !defined(LOW_MEMORY)
int ast_find_lock_info(void *lock_addr, char *filename, size_t filename_size, int *lineno, char *func, size_t func_size, char *mutex_name, size_t mutex_name_size);
#else
#define ast_find_lock_info(a,b,c,d,e,f,g,h) -1
#endif

/*!
 * \brief Unlock a lock briefly
 *
 * used during deadlock avoidance, to preserve the original location where
 * a lock was originally acquired.
 */
#define CHANNEL_DEADLOCK_AVOIDANCE(chan) \
	do { \
		char __filename[80], __func[80], __mutex_name[80]; \
		int __lineno; \
		int __res = ast_find_lock_info(&chan->lock_dont_use, __filename, sizeof(__filename), &__lineno, __func, sizeof(__func), __mutex_name, sizeof(__mutex_name)); \
		ast_channel_unlock(chan); \
		usleep(1); \
		if (__res < 0) { /* Shouldn't ever happen, but just in case... */ \
			ast_channel_lock(chan); \
		} else { \
			__ast_pthread_mutex_lock(__filename, __lineno, __func, __mutex_name, &chan->lock_dont_use); \
		} \
	} while (0)

#define DEADLOCK_AVOIDANCE(lock) \
	do { \
		char __filename[80], __func[80], __mutex_name[80]; \
		int __lineno; \
		int __res = ast_find_lock_info(lock, __filename, sizeof(__filename), &__lineno, __func, sizeof(__func), __mutex_name, sizeof(__mutex_name)); \
		ast_mutex_unlock(lock); \
		usleep(1); \
		if (__res < 0) { /* Shouldn't ever happen, but just in case... */ \
			ast_mutex_lock(lock); \
		} else { \
			__ast_pthread_mutex_lock(__filename, __lineno, __func, __mutex_name, lock); \
		} \
	} while (0)

static void __attribute__((constructor)) init_empty_mutex(void)
{
	memset(&empty_mutex, 0, sizeof(empty_mutex));
}

static inline void ast_reentrancy_lock(ast_mutex_t *p_ast_mutex)
{
	pthread_mutex_lock(&p_ast_mutex->reentr_mutex);
}

static inline void ast_reentrancy_unlock(ast_mutex_t *p_ast_mutex)
{
	pthread_mutex_unlock(&p_ast_mutex->reentr_mutex);
}

static inline void ast_reentrancy_init(ast_mutex_t *p_ast_mutex)
{
	int i;
	pthread_mutexattr_t reentr_attr;

	for (i = 0; i < AST_MAX_REENTRANCY; i++) {
		p_ast_mutex->file[i] = NULL;
		p_ast_mutex->lineno[i] = 0;
		p_ast_mutex->func[i] = NULL;
		p_ast_mutex->thread[i] = 0;
	}

	p_ast_mutex->reentrancy = 0;

	pthread_mutexattr_init(&reentr_attr);
	pthread_mutexattr_settype(&reentr_attr, AST_MUTEX_KIND);
	pthread_mutex_init(&p_ast_mutex->reentr_mutex, &reentr_attr);
	pthread_mutexattr_destroy(&reentr_attr);
}

static inline void delete_reentrancy_cs(ast_mutex_t * p_ast_mutex)
{
	pthread_mutex_destroy(&p_ast_mutex->reentr_mutex);
}

static inline int __ast_pthread_mutex_init(int track, const char *filename, int lineno, const char *func,
						const char *mutex_name, ast_mutex_t *t) 
{
	int res;
	pthread_mutexattr_t  attr;

#ifdef AST_MUTEX_INIT_W_CONSTRUCTORS

	if ((t->mutex) != ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
/*
		int canlog = strcmp(filename, "logger.c") & track;
		__ast_mutex_logger("%s line %d (%s): NOTICE: mutex '%s' is already initialized.\n",
				   filename, lineno, func, mutex_name);
		DO_THREAD_CRASH;
*/
		return 0;
	}

#endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */

	ast_reentrancy_init(t);
	t->track = track;

	pthread_mutexattr_init(&attr);
	pthread_mutexattr_settype(&attr, AST_MUTEX_KIND);

	res = pthread_mutex_init(&t->mutex, &attr);
	pthread_mutexattr_destroy(&attr);
	return res;
}

#define ast_mutex_init(pmutex) __ast_pthread_mutex_init(1, __FILE__, __LINE__, __PRETTY_FUNCTION__, #pmutex, pmutex)
#define ast_mutex_init_notracking(pmutex) \
	__ast_pthread_mutex_init(0, __FILE__, __LINE__, __PRETTY_FUNCTION__, #pmutex, pmutex)

static inline int __ast_pthread_mutex_destroy(const char *filename, int lineno, const char *func,
						const char *mutex_name, ast_mutex_t *t)
{
	int res;
	int canlog = strcmp(filename, "logger.c") & t->track;

#ifdef AST_MUTEX_INIT_W_CONSTRUCTORS
	if ((t->mutex) == ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
		/* Don't try to uninitialize non initialized mutex
		 * This may no effect on linux
		 * And always ganerate core on *BSD with 
		 * linked libpthread
		 * This not error condition if the mutex created on the fly.
		 */
		__ast_mutex_logger("%s line %d (%s): NOTICE: mutex '%s' is uninitialized.\n",
				   filename, lineno, func, mutex_name);
		return 0;
	}
#endif

	res = pthread_mutex_trylock(&t->mutex);
	switch (res) {
	case 0:
		pthread_mutex_unlock(&t->mutex);
		break;
	case EINVAL:
		__ast_mutex_logger("%s line %d (%s): Error: attempt to destroy invalid mutex '%s'.\n",
				  filename, lineno, func, mutex_name);
		break;
	case EBUSY:
		__ast_mutex_logger("%s line %d (%s): Error: attempt to destroy locked mutex '%s'.\n",
				   filename, lineno, func, mutex_name);
		ast_reentrancy_lock(t);
		__ast_mutex_logger("%s line %d (%s): Error: '%s' was locked here.\n",
			    t->file[t->reentrancy-1], t->lineno[t->reentrancy-1], t->func[t->reentrancy-1], mutex_name);
		ast_reentrancy_unlock(t);
		break;
	}

	if ((res = pthread_mutex_destroy(&t->mutex)))
		__ast_mutex_logger("%s line %d (%s): Error destroying mutex %s: %s\n",
				   filename, lineno, func, mutex_name, strerror(res));
#ifndef PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
	else
		t->mutex = PTHREAD_MUTEX_INIT_VALUE;
#endif
	ast_reentrancy_lock(t);
	t->file[0] = filename;
	t->lineno[0] = lineno;
	t->func[0] = func;
	t->reentrancy = 0;
	t->thread[0] = 0;
	ast_reentrancy_unlock(t);
	delete_reentrancy_cs(t);

	return res;
}

static inline int __ast_pthread_mutex_lock(const char *filename, int lineno, const char *func,
                                           const char* mutex_name, ast_mutex_t *t)
{
	int res;
	int canlog = strcmp(filename, "logger.c") & t->track;

#if defined(AST_MUTEX_INIT_W_CONSTRUCTORS)
	if ((t->mutex) == ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
		/* Don't warn abount uninitialized mutex.
		 * Simple try to initialize it.
		 * May be not needed in linux system.
		 */
		res = __ast_pthread_mutex_init(t->track, filename, lineno, func, mutex_name, t);
		if ((t->mutex) == ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
			__ast_mutex_logger("%s line %d (%s): Error: mutex '%s' is uninitialized and unable to initialize.\n",
					 filename, lineno, func, mutex_name);
			return res;
		}		
	}
#endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */

	if (t->track)
		ast_store_lock_info(AST_MUTEX, filename, lineno, func, mutex_name, &t->mutex);

#ifdef DETECT_DEADLOCKS
	{
		time_t seconds = time(NULL);
		time_t wait_time, reported_wait = 0;
		do {
#ifdef	HAVE_MTX_PROFILE
			ast_mark(mtx_prof, 1);
#endif
			res = pthread_mutex_trylock(&t->mutex);
#ifdef	HAVE_MTX_PROFILE
			ast_mark(mtx_prof, 0);
#endif
			if (res == EBUSY) {
				wait_time = time(NULL) - seconds;
				if (wait_time > reported_wait && (wait_time % 5) == 0) {
					__ast_mutex_logger("%s line %d (%s): Deadlock? waited %d sec for mutex '%s'?\n",
							   filename, lineno, func, (int) wait_time, mutex_name);
					ast_reentrancy_lock(t);
					__ast_mutex_logger("%s line %d (%s): '%s' was locked here.\n",
							   t->file[t->reentrancy-1], t->lineno[t->reentrancy-1],
							   t->func[t->reentrancy-1], mutex_name);
					ast_reentrancy_unlock(t);
					reported_wait = wait_time;
				}
				usleep(200);
			}
		} while (res == EBUSY);
	}
#else
#ifdef	HAVE_MTX_PROFILE
	ast_mark(mtx_prof, 1);
	res = pthread_mutex_trylock(&t->mutex);
	ast_mark(mtx_prof, 0);
	if (res)
#endif
	res = pthread_mutex_lock(&t->mutex);
#endif /* DETECT_DEADLOCKS */