threads.c

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/**
 * threads.c: set of generic threading related routines 
 *
 * See Copyright for the status of this software.
 *
 * Gary Pennington <[e-mail]>
 * [e-mail]
 */

#define IN_LIBXML
#include "libxml.h"

#include <string.h>

#include <libxml/threads.h>
#include <libxml/globals.h>

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_PTHREAD_H
#include <pthread.h>
#endif

#ifdef HAVE_WIN32_THREADS
#include <windows.h>
#ifndef HAVE_COMPILER_TLS
#include <process.h>
#endif
#endif

#ifdef HAVE_BEOS_THREADS
#include <OS.h>
#include <TLS.h>
#endif

#if defined(SOLARIS)
#include <note.h>
#endif

/* #define DEBUG_THREADS */

#ifdef HAVE_PTHREAD_H

static int libxml_is_threaded = -1;
#ifdef __GNUC__
#ifdef linux
#if (__GNUC__ == 3 && __GNUC_MINOR__ >= 3) || (__GNUC__ > 3)
extern int pthread_once (pthread_once_t *__once_control,
                         void (*__init_routine) (void))
	   __attribute((weak));
extern void *pthread_getspecific (pthread_key_t __key)
	   __attribute((weak));
extern int pthread_setspecific (pthread_key_t __key,
                                __const void *__pointer)
	   __attribute((weak));
extern int pthread_key_create (pthread_key_t *__key,
                               void (*__destr_function) (void *))
	   __attribute((weak));
extern int pthread_mutex_init ()
	   __attribute((weak));
extern int pthread_mutex_destroy ()
	   __attribute((weak));
extern int pthread_mutex_lock ()
	   __attribute((weak));
extern int pthread_mutex_unlock ()
	   __attribute((weak));
extern int pthread_cond_init ()
	   __attribute((weak));
extern int pthread_equal ()
	   __attribute((weak));
extern pthread_t pthread_self ()
	   __attribute((weak));
extern int pthread_key_create ()
	   __attribute((weak));
extern int pthread_cond_signal ()
	   __attribute((weak));
#endif
#endif /* linux */
#endif /* __GNUC__ */
#endif /* HAVE_PTHREAD_H */

/*
 * TODO: this module still uses malloc/free and not xmlMalloc/xmlFree
 *       to avoid some crazyness since xmlMalloc/xmlFree may actually
 *       be hosted on allocated blocks needing them for the allocation ...
 */

/*
 * xmlMutex are a simple mutual exception locks
 */
struct _xmlMutex {
#ifdef HAVE_PTHREAD_H
    pthread_mutex_t lock;
#elif defined HAVE_WIN32_THREADS
    HANDLE mutex;
#elif defined HAVE_BEOS_THREADS
	sem_id sem;
	thread_id tid;
#else
    int empty;
#endif
};

/*
 * xmlRMutex are reentrant mutual exception locks
 */
struct _xmlRMutex {
#ifdef HAVE_PTHREAD_H
    pthread_mutex_t lock;
    unsigned int    held;
    unsigned int    waiters;
    pthread_t       tid;
    pthread_cond_t  cv;
#elif defined HAVE_WIN32_THREADS
    CRITICAL_SECTION cs;
    unsigned int count;
#elif defined HAVE_BEOS_THREADS
	xmlMutexPtr lock;
	thread_id tid;
	int32 count;
#else
    int empty;
#endif
};
/*
 * This module still has some internal static data.
 *   - xmlLibraryLock a global lock
 *   - globalkey used for per-thread data
 */

#ifdef HAVE_PTHREAD_H
static pthread_key_t	globalkey;
static pthread_t	mainthread;
static pthread_once_t once_control = PTHREAD_ONCE_INIT;
#elif defined HAVE_WIN32_THREADS
#if defined(HAVE_COMPILER_TLS)
static __declspec(thread) xmlGlobalState tlstate;
static __declspec(thread) int tlstate_inited = 0;
#else /* HAVE_COMPILER_TLS */
static DWORD globalkey = TLS_OUT_OF_INDEXES;
#endif /* HAVE_COMPILER_TLS */
static DWORD mainthread;
static struct
{
    DWORD done;
    DWORD control;
} run_once = { 0, 0 };
/* endif HAVE_WIN32_THREADS */
#elif defined HAVE_BEOS_THREADS
int32 globalkey = 0;
thread_id mainthread = 0;
int32 run_once_init = 0;
#endif

static xmlRMutexPtr	xmlLibraryLock = NULL;
#ifdef LIBXML_THREAD_ENABLED
static void xmlOnceInit(void);
#endif

/**
 * xmlNewMutex:
 *
 * xmlNewMutex() is used to allocate a libxml2 token struct for use in
 * synchronizing access to data.
 *
 * Returns a new simple mutex pointer or NULL in case of error
 */
xmlMutexPtr
xmlNewMutex(void)
{
    xmlMutexPtr tok;

    if ((tok = malloc(sizeof(xmlMutex))) == NULL)
        return (NULL);
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded != 0)
	pthread_mutex_init(&tok->lock, NULL);
#elif defined HAVE_WIN32_THREADS
    tok->mutex = CreateMutex(NULL, FALSE, NULL);
#elif defined HAVE_BEOS_THREADS
	if ((tok->sem = create_sem(1, "xmlMutex")) < B_OK) {
		free(tok);
		return NULL;
	}
	tok->tid = -1;
#endif
    return (tok);
}

/**
 * xmlFreeMutex:
 * @tok:  the simple mutex
 *
 * xmlFreeMutex() is used to reclaim resources associated with a libxml2 token
 * struct.
 */
void
xmlFreeMutex(xmlMutexPtr tok)
{
    if (tok == NULL) return;

#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded != 0)
	pthread_mutex_destroy(&tok->lock);
#elif defined HAVE_WIN32_THREADS
    CloseHandle(tok->mutex);
#elif defined HAVE_BEOS_THREADS
	delete_sem(tok->sem);
#endif
    free(tok);
}

/**
 * xmlMutexLock:
 * @tok:  the simple mutex
 *
 * xmlMutexLock() is used to lock a libxml2 token.
 */
void
xmlMutexLock(xmlMutexPtr tok)
{
    if (tok == NULL)
        return;
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded != 0)
	pthread_mutex_lock(&tok->lock);
#elif defined HAVE_WIN32_THREADS
    WaitForSingleObject(tok->mutex, INFINITE);
#elif defined HAVE_BEOS_THREADS
	if (acquire_sem(tok->sem) != B_NO_ERROR) {
#ifdef DEBUG_THREADS
		xmlGenericError(xmlGenericErrorContext, "xmlMutexLock():BeOS:Couldn't aquire semaphore\n");
		exit();
#endif
	}
	tok->tid = find_thread(NULL);
#endif

}

/**
 * xmlMutexUnlock:
 * @tok:  the simple mutex
 *
 * xmlMutexUnlock() is used to unlock a libxml2 token.
 */
void
xmlMutexUnlock(xmlMutexPtr tok)
{
    if (tok == NULL)
        return;
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded != 0)
	pthread_mutex_unlock(&tok->lock);
#elif defined HAVE_WIN32_THREADS
    ReleaseMutex(tok->mutex);
#elif defined HAVE_BEOS_THREADS
	if (tok->tid == find_thread(NULL)) {
		tok->tid = -1;
		release_sem(tok->sem);
	}
#endif
}

/**
 * xmlNewRMutex:
 *
 * xmlRNewMutex() is used to allocate a reentrant mutex for use in
 * synchronizing access to data. token_r is a re-entrant lock and thus useful
 * for synchronizing access to data structures that may be manipulated in a
 * recursive fashion.
 *
 * Returns the new reentrant mutex pointer or NULL in case of error
 */
xmlRMutexPtr
xmlNewRMutex(void)
{
    xmlRMutexPtr tok;

    if ((tok = malloc(sizeof(xmlRMutex))) == NULL)
        return (NULL);
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded != 0) {
	pthread_mutex_init(&tok->lock, NULL);
	tok->held = 0;
	tok->waiters = 0;
	pthread_cond_init(&tok->cv, NULL);
    }
#elif defined HAVE_WIN32_THREADS
    InitializeCriticalSection(&tok->cs);
    tok->count = 0;
#elif defined HAVE_BEOS_THREADS
	if ((tok->lock = xmlNewMutex()) == NULL) {
		free(tok);
		return NULL;
	}
	tok->count = 0;
#endif
    return (tok);
}

/**
 * xmlFreeRMutex:
 * @tok:  the reentrant mutex
 *
 * xmlRFreeMutex() is used to reclaim resources associated with a
 * reentrant mutex.
 */
void
xmlFreeRMutex(xmlRMutexPtr tok ATTRIBUTE_UNUSED)
{
    if (tok == NULL)
        return;
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded != 0)
	pthread_mutex_destroy(&tok->lock);
#elif defined HAVE_WIN32_THREADS
    DeleteCriticalSection(&tok->cs);
#elif defined HAVE_BEOS_THREADS
	xmlFreeMutex(tok->lock);
#endif
    free(tok);
}

/**
 * xmlRMutexLock:
 * @tok:  the reentrant mutex
 *
 * xmlRMutexLock() is used to lock a libxml2 token_r.
 */
void
xmlRMutexLock(xmlRMutexPtr tok)
{
    if (tok == NULL)
        return;
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded == 0)
        return;

    pthread_mutex_lock(&tok->lock);
    if (tok->held) {
        if (pthread_equal(tok->tid, pthread_self())) {
            tok->held++;
            pthread_mutex_unlock(&tok->lock);
            return;
        } else {
            tok->waiters++;
            while (tok->held)
                pthread_cond_wait(&tok->cv, &tok->lock);
            tok->waiters--;
        }
    }
    tok->tid = pthread_self();
    tok->held = 1;
    pthread_mutex_unlock(&tok->lock);
#elif defined HAVE_WIN32_THREADS
    EnterCriticalSection(&tok->cs);
    ++tok->count;
#elif defined HAVE_BEOS_THREADS
	if (tok->lock->tid == find_thread(NULL)) {
		tok->count++;
		return;
	} else {
		xmlMutexLock(tok->lock);
		tok->count = 1;
	}
#endif
}

/**
 * xmlRMutexUnlock:
 * @tok:  the reentrant mutex
 *
 * xmlRMutexUnlock() is used to unlock a libxml2 token_r.
 */
void
xmlRMutexUnlock(xmlRMutexPtr tok ATTRIBUTE_UNUSED)
{
    if (tok == NULL)
        return;
#ifdef HAVE_PTHREAD_H
    if (libxml_is_threaded == 0)
        return;
    
    pthread_mutex_lock(&tok->lock);
    tok->held--;
    if (tok->held == 0) {
        if (tok->waiters)
            pthread_cond_signal(&tok->cv);
        tok->tid = 0;
    }
    pthread_mutex_unlock(&tok->lock);
#elif defined HAVE_WIN32_THREADS
    if (!--tok->count) 
	LeaveCriticalSection(&tok->cs);
#elif defined HAVE_BEOS_THREADS
	if (tok->lock->tid == find_thread(NULL)) {
		tok->count--;
		if (tok->count == 0) {
			xmlMutexUnlock(tok->lock);
		}
		return;
	}
#endif
}

/************************************************************************
 *									*
 *			Per thread global state handling		*
 *									*
 ************************************************************************/

#ifdef LIBXML_THREAD_ENABLED
#ifdef xmlLastError
#undef xmlLastError
#endif
/**
 * xmlFreeGlobalState:
 * @state:  a thread global state
 *
 * xmlFreeGlobalState() is called when a thread terminates with a non-NULL
 * global state. It is is used here to reclaim memory resources.
 */
static void
xmlFreeGlobalState(void *state)
{