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cpython/Python/thread_pthread.h

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/* Posix threads interface */
#include <stdlib.h>
#include <string.h>
#if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
#define destructor xxdestructor
#endif
#include <pthread.h>
#if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
#undef destructor
#endif
#include <signal.h>
/* The POSIX spec says that implementations supporting the sem_*
family of functions must indicate this by defining
_POSIX_SEMAPHORES. */
#ifdef _POSIX_SEMAPHORES
#include <semaphore.h>
#include <errno.h>
#endif
#if !defined(pthread_attr_default)
# define pthread_attr_default ((pthread_attr_t *)NULL)
#endif
#if !defined(pthread_mutexattr_default)
# define pthread_mutexattr_default ((pthread_mutexattr_t *)NULL)
#endif
#if !defined(pthread_condattr_default)
# define pthread_condattr_default ((pthread_condattr_t *)NULL)
#endif
/* Whether or not to use semaphores directly rather than emulating them with
* mutexes and condition variables:
*/
#if defined(_POSIX_SEMAPHORES) && !defined(HAVE_BROKEN_POSIX_SEMAPHORES)
# define USE_SEMAPHORES
#else
# undef USE_SEMAPHORES
#endif
/* On platforms that don't use standard POSIX threads pthread_sigmask()
* isn't present. DEC threads uses sigprocmask() instead as do most
* other UNIX International compliant systems that don't have the full
* pthread implementation.
*/
#if defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
# define SET_THREAD_SIGMASK pthread_sigmask
#else
# define SET_THREAD_SIGMASK sigprocmask
#endif
/* A pthread mutex isn't sufficient to model the Python lock type
* because, according to Draft 5 of the docs (P1003.4a/D5), both of the
* following are undefined:
* -> a thread tries to lock a mutex it already has locked
* -> a thread tries to unlock a mutex locked by a different thread
* pthread mutexes are designed for serializing threads over short pieces
* of code anyway, so wouldn't be an appropriate implementation of
* Python's locks regardless.
*
* The pthread_lock struct implements a Python lock as a "locked?" bit
* and a <condition, mutex> pair. In general, if the bit can be acquired
* instantly, it is, else the pair is used to block the thread until the
* bit is cleared. 9 May 1994 tim@ksr.com
*/
typedef struct {
char locked; /* 0=unlocked, 1=locked */
/* a <cond, mutex> pair to handle an acquire of a locked lock */
pthread_cond_t lock_released;
pthread_mutex_t mut;
} pthread_lock;
#define CHECK_STATUS(name) if (status != 0) { perror(name); error = 1; }
/*
* Initialization.
*/
#ifdef _HAVE_BSDI
static
void _noop(void)
{
}
static void
PyThread__init_thread(void)
{
/* DO AN INIT BY STARTING THE THREAD */
static int dummy = 0;
pthread_t thread1;
pthread_create(&thread1, NULL, (void *) _noop, &dummy);
pthread_join(thread1, NULL);
}
#else /* !_HAVE_BSDI */
static void
PyThread__init_thread(void)
{
#if defined(_AIX) && defined(__GNUC__)
pthread_init();
#endif
}
#endif /* !_HAVE_BSDI */
/*
* Thread support.
*/
long
PyThread_start_new_thread(void (*func)(void *), void *arg)
{
pthread_t th;
int status;
sigset_t oldmask, newmask;
#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
pthread_attr_t attrs;
#endif
dprintf(("PyThread_start_new_thread called\n"));
if (!initialized)
PyThread_init_thread();
#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
pthread_attr_init(&attrs);
#endif
#ifdef THREAD_STACK_SIZE
pthread_attr_setstacksize(&attrs, THREAD_STACK_SIZE);
#endif
#if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED) && !defined(__FreeBSD__)
pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
#endif
/* Mask all signals in the current thread before creating the new
* thread. This causes the new thread to start with all signals
* blocked.
*/
sigfillset(&newmask);
SET_THREAD_SIGMASK(SIG_BLOCK, &newmask, &oldmask);
status = pthread_create(&th,
#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
&attrs,
#else
(pthread_attr_t*)NULL,
#endif
(void* (*)(void *))func,
(void *)arg
);
/* Restore signal mask for original thread */
SET_THREAD_SIGMASK(SIG_SETMASK, &oldmask, NULL);
#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
pthread_attr_destroy(&attrs);
#endif
if (status != 0)
return -1;
pthread_detach(th);
#if SIZEOF_PTHREAD_T <= SIZEOF_LONG
return (long) th;
#else
return (long) *(long *) &th;
#endif
}
/* XXX This implementation is considered (to quote Tim Peters) "inherently
hosed" because:
- It does not guarantee the promise that a non-zero integer is returned.
- The cast to long is inherently unsafe.
- It is not clear that the 'volatile' (for AIX?) and ugly casting in the
latter return statement (for Alpha OSF/1) are any longer necessary.
*/
long
PyThread_get_thread_ident(void)
{
volatile pthread_t threadid;
if (!initialized)
PyThread_init_thread();
/* Jump through some hoops for Alpha OSF/1 */
threadid = pthread_self();
#if SIZEOF_PTHREAD_T <= SIZEOF_LONG
return (long) threadid;
#else
return (long) *(long *) &threadid;
#endif
}
static void
do_PyThread_exit_thread(int no_cleanup)
{
dprintf(("PyThread_exit_thread called\n"));
if (!initialized) {
if (no_cleanup)
_exit(0);
else
exit(0);
}
}
void
PyThread_exit_thread(void)
{
do_PyThread_exit_thread(0);
}
void
PyThread__exit_thread(void)
{
do_PyThread_exit_thread(1);
}
#ifndef NO_EXIT_PROG
static void
do_PyThread_exit_prog(int status, int no_cleanup)
{
dprintf(("PyThread_exit_prog(%d) called\n", status));
if (!initialized)
if (no_cleanup)
_exit(status);
else
exit(status);
}
void
PyThread_exit_prog(int status)
{
do_PyThread_exit_prog(status, 0);
}
void
PyThread__exit_prog(int status)
{
do_PyThread_exit_prog(status, 1);
}
#endif /* NO_EXIT_PROG */
#ifdef USE_SEMAPHORES
/*
* Lock support.
*/
PyThread_type_lock
PyThread_allocate_lock(void)
{
sem_t *lock;
int status, error = 0;
dprintf(("PyThread_allocate_lock called\n"));
if (!initialized)
PyThread_init_thread();
lock = (sem_t *)malloc(sizeof(sem_t));
if (lock) {
status = sem_init(lock,0,1);
CHECK_STATUS("sem_init");
if (error) {
free((void *)lock);
lock = NULL;
}
}
dprintf(("PyThread_allocate_lock() -> %p\n", lock));
return (PyThread_type_lock)lock;
}
void
PyThread_free_lock(PyThread_type_lock lock)
{
sem_t *thelock = (sem_t *)lock;
int status, error = 0;
dprintf(("PyThread_free_lock(%p) called\n", lock));
if (!thelock)
return;
status = sem_destroy(thelock);
CHECK_STATUS("sem_destroy");
free((void *)thelock);
}
/*
* As of February 2002, Cygwin thread implementations mistakenly report error
* codes in the return value of the sem_ calls (like the pthread_ functions).
* Correct implementations return -1 and put the code in errno. This supports
* either.
*/
static int
fix_status(int status)
{
return (status == -1) ? errno : status;
}
int
PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
{
int success;
sem_t *thelock = (sem_t *)lock;
int status, error = 0;
dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
do {
if (waitflag)
status = fix_status(sem_wait(thelock));
else
status = fix_status(sem_trywait(thelock));
} while (status == EINTR); /* Retry if interrupted by a signal */
if (waitflag) {
CHECK_STATUS("sem_wait");
} else if (status != EAGAIN) {
CHECK_STATUS("sem_trywait");
}
success = (status == 0) ? 1 : 0;
dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
return success;
}
void
PyThread_release_lock(PyThread_type_lock lock)
{
sem_t *thelock = (sem_t *)lock;
int status, error = 0;
dprintf(("PyThread_release_lock(%p) called\n", lock));
status = sem_post(thelock);
CHECK_STATUS("sem_post");
}
#else /* USE_SEMAPHORES */
/*
* Lock support.
*/
PyThread_type_lock
PyThread_allocate_lock(void)
{
pthread_lock *lock;
int status, error = 0;
dprintf(("PyThread_allocate_lock called\n"));
if (!initialized)
PyThread_init_thread();
lock = (pthread_lock *) malloc(sizeof(pthread_lock));
memset((void *)lock, '\0', sizeof(pthread_lock));
if (lock) {
lock->locked = 0;
status = pthread_mutex_init(&lock->mut,
pthread_mutexattr_default);
CHECK_STATUS("pthread_mutex_init");
status = pthread_cond_init(&lock->lock_released,
pthread_condattr_default);
CHECK_STATUS("pthread_cond_init");
if (error) {
free((void *)lock);
lock = 0;
}
}
dprintf(("PyThread_allocate_lock() -> %p\n", lock));
return (PyThread_type_lock) lock;
}
void
PyThread_free_lock(PyThread_type_lock lock)
{
pthread_lock *thelock = (pthread_lock *)lock;
int status, error = 0;
dprintf(("PyThread_free_lock(%p) called\n", lock));
status = pthread_mutex_destroy( &thelock->mut );
CHECK_STATUS("pthread_mutex_destroy");
status = pthread_cond_destroy( &thelock->lock_released );
CHECK_STATUS("pthread_cond_destroy");
free((void *)thelock);
}
int
PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
{
int success;
pthread_lock *thelock = (pthread_lock *)lock;
int status, error = 0;
dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
status = pthread_mutex_lock( &thelock->mut );
CHECK_STATUS("pthread_mutex_lock[1]");
success = thelock->locked == 0;
if ( !success && waitflag ) {
/* continue trying until we get the lock */
/* mut must be locked by me -- part of the condition
* protocol */
while ( thelock->locked ) {
status = pthread_cond_wait(&thelock->lock_released,
&thelock->mut);
CHECK_STATUS("pthread_cond_wait");
}
success = 1;
}
if (success) thelock->locked = 1;
status = pthread_mutex_unlock( &thelock->mut );
CHECK_STATUS("pthread_mutex_unlock[1]");
if (error) success = 0;
dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
return success;
}
void
PyThread_release_lock(PyThread_type_lock lock)
{
pthread_lock *thelock = (pthread_lock *)lock;
int status, error = 0;
dprintf(("PyThread_release_lock(%p) called\n", lock));
status = pthread_mutex_lock( &thelock->mut );
CHECK_STATUS("pthread_mutex_lock[3]");
thelock->locked = 0;
status = pthread_mutex_unlock( &thelock->mut );
CHECK_STATUS("pthread_mutex_unlock[3]");
/* wake up someone (anyone, if any) waiting on the lock */
status = pthread_cond_signal( &thelock->lock_released );
CHECK_STATUS("pthread_cond_signal");
}
#endif /* USE_SEMAPHORES */
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