mirror of
https://github.com/python/cpython
synced 2024-09-05 16:38:56 +00:00
453 lines
10 KiB
C
453 lines
10 KiB
C
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/* Posix threads interface */
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#include <stdlib.h>
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#include <string.h>
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#if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
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#define destructor xxdestructor
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#endif
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#include <pthread.h>
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#if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
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#undef destructor
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#endif
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#include <signal.h>
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/* The POSIX spec says that implementations supporting the sem_*
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family of functions must indicate this by defining
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_POSIX_SEMAPHORES. */
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#ifdef _POSIX_SEMAPHORES
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/* On FreeBSD 4.x, _POSIX_SEMAPHORES is defined empty, so
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we need to add 0 to make it work there as well. */
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#if (_POSIX_SEMAPHORES+0) == -1
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#define HAVE_BROKEN_POSIX_SEMAPHORES
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#else
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#include <semaphore.h>
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#include <errno.h>
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#endif
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#endif
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#if !defined(pthread_attr_default)
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# define pthread_attr_default ((pthread_attr_t *)NULL)
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#endif
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#if !defined(pthread_mutexattr_default)
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# define pthread_mutexattr_default ((pthread_mutexattr_t *)NULL)
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#endif
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#if !defined(pthread_condattr_default)
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# define pthread_condattr_default ((pthread_condattr_t *)NULL)
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#endif
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/* Whether or not to use semaphores directly rather than emulating them with
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* mutexes and condition variables:
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*/
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#if defined(_POSIX_SEMAPHORES) && !defined(HAVE_BROKEN_POSIX_SEMAPHORES)
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# define USE_SEMAPHORES
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#else
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# undef USE_SEMAPHORES
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#endif
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/* On platforms that don't use standard POSIX threads pthread_sigmask()
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* isn't present. DEC threads uses sigprocmask() instead as do most
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* other UNIX International compliant systems that don't have the full
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* pthread implementation.
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*/
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#if defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
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# define SET_THREAD_SIGMASK pthread_sigmask
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#else
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# define SET_THREAD_SIGMASK sigprocmask
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#endif
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/* A pthread mutex isn't sufficient to model the Python lock type
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* because, according to Draft 5 of the docs (P1003.4a/D5), both of the
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* following are undefined:
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* -> a thread tries to lock a mutex it already has locked
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* -> a thread tries to unlock a mutex locked by a different thread
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* pthread mutexes are designed for serializing threads over short pieces
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* of code anyway, so wouldn't be an appropriate implementation of
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* Python's locks regardless.
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*
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* The pthread_lock struct implements a Python lock as a "locked?" bit
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* and a <condition, mutex> pair. In general, if the bit can be acquired
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* instantly, it is, else the pair is used to block the thread until the
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* bit is cleared. 9 May 1994 tim@ksr.com
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*/
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typedef struct {
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char locked; /* 0=unlocked, 1=locked */
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/* a <cond, mutex> pair to handle an acquire of a locked lock */
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pthread_cond_t lock_released;
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pthread_mutex_t mut;
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} pthread_lock;
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#define CHECK_STATUS(name) if (status != 0) { perror(name); error = 1; }
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/*
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* Initialization.
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*/
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#ifdef _HAVE_BSDI
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static
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void _noop(void)
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{
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}
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static void
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PyThread__init_thread(void)
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{
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/* DO AN INIT BY STARTING THE THREAD */
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static int dummy = 0;
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pthread_t thread1;
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pthread_create(&thread1, NULL, (void *) _noop, &dummy);
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pthread_join(thread1, NULL);
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}
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#else /* !_HAVE_BSDI */
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static void
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PyThread__init_thread(void)
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{
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#if defined(_AIX) && defined(__GNUC__)
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pthread_init();
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#endif
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}
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#endif /* !_HAVE_BSDI */
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/*
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* Thread support.
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*/
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long
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PyThread_start_new_thread(void (*func)(void *), void *arg)
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{
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pthread_t th;
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int status;
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#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
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pthread_attr_t attrs;
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#endif
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dprintf(("PyThread_start_new_thread called\n"));
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if (!initialized)
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PyThread_init_thread();
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#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
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pthread_attr_init(&attrs);
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#endif
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#ifdef THREAD_STACK_SIZE
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pthread_attr_setstacksize(&attrs, THREAD_STACK_SIZE);
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#endif
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#if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED) && !defined(__FreeBSD__)
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pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
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#endif
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status = pthread_create(&th,
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#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
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&attrs,
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#else
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(pthread_attr_t*)NULL,
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#endif
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(void* (*)(void *))func,
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(void *)arg
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);
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#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
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pthread_attr_destroy(&attrs);
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#endif
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if (status != 0)
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return -1;
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pthread_detach(th);
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#if SIZEOF_PTHREAD_T <= SIZEOF_LONG
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return (long) th;
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#else
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return (long) *(long *) &th;
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#endif
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}
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/* XXX This implementation is considered (to quote Tim Peters) "inherently
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hosed" because:
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- It does not guarantee the promise that a non-zero integer is returned.
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- The cast to long is inherently unsafe.
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- It is not clear that the 'volatile' (for AIX?) and ugly casting in the
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latter return statement (for Alpha OSF/1) are any longer necessary.
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*/
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long
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PyThread_get_thread_ident(void)
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{
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volatile pthread_t threadid;
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if (!initialized)
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PyThread_init_thread();
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/* Jump through some hoops for Alpha OSF/1 */
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threadid = pthread_self();
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#if SIZEOF_PTHREAD_T <= SIZEOF_LONG
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return (long) threadid;
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#else
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return (long) *(long *) &threadid;
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#endif
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}
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static void
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do_PyThread_exit_thread(int no_cleanup)
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{
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dprintf(("PyThread_exit_thread called\n"));
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if (!initialized) {
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if (no_cleanup)
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_exit(0);
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else
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exit(0);
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}
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}
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void
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PyThread_exit_thread(void)
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{
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do_PyThread_exit_thread(0);
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}
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void
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PyThread__exit_thread(void)
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{
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do_PyThread_exit_thread(1);
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}
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#ifndef NO_EXIT_PROG
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static void
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do_PyThread_exit_prog(int status, int no_cleanup)
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{
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dprintf(("PyThread_exit_prog(%d) called\n", status));
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if (!initialized)
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if (no_cleanup)
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_exit(status);
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else
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exit(status);
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}
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void
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PyThread_exit_prog(int status)
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{
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do_PyThread_exit_prog(status, 0);
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}
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void
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PyThread__exit_prog(int status)
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{
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do_PyThread_exit_prog(status, 1);
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}
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#endif /* NO_EXIT_PROG */
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#ifdef USE_SEMAPHORES
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/*
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* Lock support.
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*/
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PyThread_type_lock
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PyThread_allocate_lock(void)
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{
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sem_t *lock;
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int status, error = 0;
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dprintf(("PyThread_allocate_lock called\n"));
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if (!initialized)
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PyThread_init_thread();
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lock = (sem_t *)malloc(sizeof(sem_t));
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if (lock) {
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status = sem_init(lock,0,1);
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CHECK_STATUS("sem_init");
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if (error) {
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free((void *)lock);
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lock = NULL;
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}
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}
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dprintf(("PyThread_allocate_lock() -> %p\n", lock));
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return (PyThread_type_lock)lock;
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}
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void
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PyThread_free_lock(PyThread_type_lock lock)
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{
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sem_t *thelock = (sem_t *)lock;
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int status, error = 0;
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dprintf(("PyThread_free_lock(%p) called\n", lock));
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if (!thelock)
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return;
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status = sem_destroy(thelock);
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CHECK_STATUS("sem_destroy");
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free((void *)thelock);
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}
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/*
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* As of February 2002, Cygwin thread implementations mistakenly report error
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* codes in the return value of the sem_ calls (like the pthread_ functions).
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* Correct implementations return -1 and put the code in errno. This supports
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* either.
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*/
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static int
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fix_status(int status)
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{
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return (status == -1) ? errno : status;
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}
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int
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PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
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{
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int success;
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sem_t *thelock = (sem_t *)lock;
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int status, error = 0;
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dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
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do {
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if (waitflag)
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status = fix_status(sem_wait(thelock));
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else
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status = fix_status(sem_trywait(thelock));
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} while (status == EINTR); /* Retry if interrupted by a signal */
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if (waitflag) {
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CHECK_STATUS("sem_wait");
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} else if (status != EAGAIN) {
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CHECK_STATUS("sem_trywait");
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}
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success = (status == 0) ? 1 : 0;
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dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
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return success;
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}
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void
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PyThread_release_lock(PyThread_type_lock lock)
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{
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sem_t *thelock = (sem_t *)lock;
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int status, error = 0;
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dprintf(("PyThread_release_lock(%p) called\n", lock));
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status = sem_post(thelock);
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CHECK_STATUS("sem_post");
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}
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#else /* USE_SEMAPHORES */
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/*
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* Lock support.
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*/
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PyThread_type_lock
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PyThread_allocate_lock(void)
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{
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pthread_lock *lock;
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int status, error = 0;
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dprintf(("PyThread_allocate_lock called\n"));
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if (!initialized)
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PyThread_init_thread();
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lock = (pthread_lock *) malloc(sizeof(pthread_lock));
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if (lock) {
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memset((void *)lock, '\0', sizeof(pthread_lock));
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lock->locked = 0;
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status = pthread_mutex_init(&lock->mut,
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pthread_mutexattr_default);
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CHECK_STATUS("pthread_mutex_init");
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status = pthread_cond_init(&lock->lock_released,
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pthread_condattr_default);
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CHECK_STATUS("pthread_cond_init");
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if (error) {
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free((void *)lock);
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lock = 0;
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}
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}
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dprintf(("PyThread_allocate_lock() -> %p\n", lock));
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return (PyThread_type_lock) lock;
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}
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void
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PyThread_free_lock(PyThread_type_lock lock)
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{
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pthread_lock *thelock = (pthread_lock *)lock;
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int status, error = 0;
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dprintf(("PyThread_free_lock(%p) called\n", lock));
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status = pthread_mutex_destroy( &thelock->mut );
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CHECK_STATUS("pthread_mutex_destroy");
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status = pthread_cond_destroy( &thelock->lock_released );
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CHECK_STATUS("pthread_cond_destroy");
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free((void *)thelock);
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}
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int
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PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
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{
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int success;
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pthread_lock *thelock = (pthread_lock *)lock;
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int status, error = 0;
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dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
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status = pthread_mutex_lock( &thelock->mut );
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CHECK_STATUS("pthread_mutex_lock[1]");
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success = thelock->locked == 0;
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if ( !success && waitflag ) {
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/* continue trying until we get the lock */
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/* mut must be locked by me -- part of the condition
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* protocol */
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while ( thelock->locked ) {
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status = pthread_cond_wait(&thelock->lock_released,
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&thelock->mut);
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CHECK_STATUS("pthread_cond_wait");
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}
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success = 1;
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}
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if (success) thelock->locked = 1;
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status = pthread_mutex_unlock( &thelock->mut );
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CHECK_STATUS("pthread_mutex_unlock[1]");
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if (error) success = 0;
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dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
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return success;
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}
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void
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PyThread_release_lock(PyThread_type_lock lock)
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{
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pthread_lock *thelock = (pthread_lock *)lock;
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int status, error = 0;
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dprintf(("PyThread_release_lock(%p) called\n", lock));
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status = pthread_mutex_lock( &thelock->mut );
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CHECK_STATUS("pthread_mutex_lock[3]");
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thelock->locked = 0;
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status = pthread_mutex_unlock( &thelock->mut );
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CHECK_STATUS("pthread_mutex_unlock[3]");
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/* wake up someone (anyone, if any) waiting on the lock */
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status = pthread_cond_signal( &thelock->lock_released );
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CHECK_STATUS("pthread_cond_signal");
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}
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#endif /* USE_SEMAPHORES */
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