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cpython/Python/thread_pthread.h
Victor Stinner 590cebe391 Issue #19787: PyThread_set_key_value() now always set the value 
In Python 3.3, PyThread_set_key_value() did nothing if the key already exists
(if the current value is a non-NULL pointer).

When _PyGILState_NoteThreadState() is called twice on the same thread with a
different Python thread state, it still keeps the old Python thread state to
keep the old behaviour. Replacing the Python thread state with the new state
introduces new bugs: see issues #10915 and #15751.
2013-12-13 11:08:56 +01:00

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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 requires that use of pthread_attr_setstacksize
be conditional on _POSIX_THREAD_ATTR_STACKSIZE being defined. */
#ifdef _POSIX_THREAD_ATTR_STACKSIZE
#ifndef THREAD_STACK_SIZE
#define THREAD_STACK_SIZE 0 /* use default stack size */
#endif
/* The default stack size for new threads on OSX and BSD is small enough that
* we'll get hard crashes instead of 'maximum recursion depth exceeded'
* exceptions.
*
* The default stack sizes below are the empirically determined minimal stack
* sizes where a simple recursive function doesn't cause a hard crash.
*/
#if defined(__APPLE__) && defined(THREAD_STACK_SIZE) && THREAD_STACK_SIZE == 0
#undef THREAD_STACK_SIZE
#define THREAD_STACK_SIZE 0x500000
#endif
#if defined(__FreeBSD__) && defined(THREAD_STACK_SIZE) && THREAD_STACK_SIZE == 0
#undef THREAD_STACK_SIZE
#define THREAD_STACK_SIZE 0x400000
#endif
/* for safety, ensure a viable minimum stacksize */
#define THREAD_STACK_MIN 0x8000 /* 32kB */
#else /* !_POSIX_THREAD_ATTR_STACKSIZE */
#ifdef THREAD_STACK_SIZE
#error "THREAD_STACK_SIZE defined but _POSIX_THREAD_ATTR_STACKSIZE undefined"
#endif
#endif
/* The POSIX spec says that implementations supporting the sem_*
family of functions must indicate this by defining
_POSIX_SEMAPHORES. */
#ifdef _POSIX_SEMAPHORES
/* On FreeBSD 4.x, _POSIX_SEMAPHORES is defined empty, so
we need to add 0 to make it work there as well. */
#if (_POSIX_SEMAPHORES+0) == -1
#define HAVE_BROKEN_POSIX_SEMAPHORES
#else
#include <semaphore.h>
#include <errno.h>
#endif
#endif
/* Before FreeBSD 5.4, system scope threads was very limited resource
in default setting. So the process scope is preferred to get
enough number of threads to work. */
#ifdef __FreeBSD__
#include <osreldate.h>
#if __FreeBSD_version >= 500000 && __FreeBSD_version < 504101
#undef PTHREAD_SYSTEM_SCHED_SUPPORTED
#endif
#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) && \
defined(HAVE_SEM_TIMEDWAIT))
# 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
/* We assume all modern POSIX systems have gettimeofday() */
#ifdef GETTIMEOFDAY_NO_TZ
#define GETTIMEOFDAY(ptv) gettimeofday(ptv)
#else
#define GETTIMEOFDAY(ptv) gettimeofday(ptv, (struct timezone *)NULL)
#endif
#define MICROSECONDS_TO_TIMESPEC(microseconds, ts) \
do { \
struct timeval tv; \
GETTIMEOFDAY(&tv); \
tv.tv_usec += microseconds % 1000000; \
tv.tv_sec += microseconds / 1000000; \
tv.tv_sec += tv.tv_usec / 1000000; \
tv.tv_usec %= 1000000; \
ts.tv_sec = tv.tv_sec; \
ts.tv_nsec = tv.tv_usec * 1000; \
} while(0)
/* 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.
*/
#if defined(_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__)
extern void pthread_init(void);
pthread_init();
#endif
}
#endif /* !_HAVE_BSDI */
/*
* Thread support.
*/
long
PyThread_start_new_thread(void (*func)(void *), void *arg)
{
pthread_t th;
int status;
#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
pthread_attr_t attrs;
#endif
#if defined(THREAD_STACK_SIZE)
size_t tss;
#endif
dprintf(("PyThread_start_new_thread called\n"));
if (!initialized)
PyThread_init_thread();
#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
if (pthread_attr_init(&attrs) != 0)
return -1;
#endif
#if defined(THREAD_STACK_SIZE)
tss = (_pythread_stacksize != 0) ? _pythread_stacksize
: THREAD_STACK_SIZE;
if (tss != 0) {
if (pthread_attr_setstacksize(&attrs, tss) != 0) {
pthread_attr_destroy(&attrs);
return -1;
}
}
#endif
#if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
#endif
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
);
#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?) are any longer necessary.
*/
long
PyThread_get_thread_ident(void)
{
volatile pthread_t threadid;
if (!initialized)
PyThread_init_thread();
threadid = pthread_self();
return (long) threadid;
}
void
PyThread_exit_thread(void)
{
dprintf(("PyThread_exit_thread called\n"));
if (!initialized)
exit(0);
pthread_exit(0);
}
#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 *)PyMem_RawMalloc(sizeof(sem_t));
if (lock) {
status = sem_init(lock,0,1);
CHECK_STATUS("sem_init");
if (error) {
PyMem_RawFree((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;
(void) error; /* silence unused-but-set-variable warning */
dprintf(("PyThread_free_lock(%p) called\n", lock));
if (!thelock)
return;
status = sem_destroy(thelock);
CHECK_STATUS("sem_destroy");
PyMem_RawFree((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;
}
PyLockStatus
PyThread_acquire_lock_timed(PyThread_type_lock lock, PY_TIMEOUT_T microseconds,
int intr_flag)
{
PyLockStatus success;
sem_t *thelock = (sem_t *)lock;
int status, error = 0;
struct timespec ts;
(void) error; /* silence unused-but-set-variable warning */
dprintf(("PyThread_acquire_lock_timed(%p, %lld, %d) called\n",
lock, microseconds, intr_flag));
if (microseconds > 0)
MICROSECONDS_TO_TIMESPEC(microseconds, ts);
do {
if (microseconds > 0)
status = fix_status(sem_timedwait(thelock, &ts));
else if (microseconds == 0)
status = fix_status(sem_trywait(thelock));
else
status = fix_status(sem_wait(thelock));
/* Retry if interrupted by a signal, unless the caller wants to be
notified. */
} while (!intr_flag && status == EINTR);
/* Don't check the status if we're stopping because of an interrupt. */
if (!(intr_flag && status == EINTR)) {
if (microseconds > 0) {
if (status != ETIMEDOUT)
CHECK_STATUS("sem_timedwait");
}
else if (microseconds == 0) {
if (status != EAGAIN)
CHECK_STATUS("sem_trywait");
}
else {
CHECK_STATUS("sem_wait");
}
}
if (status == 0) {
success = PY_LOCK_ACQUIRED;
} else if (intr_flag && status == EINTR) {
success = PY_LOCK_INTR;
} else {
success = PY_LOCK_FAILURE;
}
dprintf(("PyThread_acquire_lock_timed(%p, %lld, %d) -> %d\n",
lock, microseconds, intr_flag, success));
return success;
}
void
PyThread_release_lock(PyThread_type_lock lock)
{
sem_t *thelock = (sem_t *)lock;
int status, error = 0;
(void) error; /* silence unused-but-set-variable warning */
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 *) PyMem_RawMalloc(sizeof(pthread_lock));
if (lock) {
memset((void *)lock, '\0', sizeof(pthread_lock));
lock->locked = 0;
status = pthread_mutex_init(&lock->mut,
pthread_mutexattr_default);
CHECK_STATUS("pthread_mutex_init");
/* Mark the pthread mutex underlying a Python mutex as
pure happens-before. We can't simply mark the
Python-level mutex as a mutex because it can be
acquired and released in different threads, which
will cause errors. */
_Py_ANNOTATE_PURE_HAPPENS_BEFORE_MUTEX(&lock->mut);
status = pthread_cond_init(&lock->lock_released,
pthread_condattr_default);
CHECK_STATUS("pthread_cond_init");
if (error) {
PyMem_RawFree((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;
(void) error; /* silence unused-but-set-variable warning */
dprintf(("PyThread_free_lock(%p) called\n", lock));
/* some pthread-like implementations tie the mutex to the cond
* and must have the cond destroyed first.
*/
status = pthread_cond_destroy( &thelock->lock_released );
CHECK_STATUS("pthread_cond_destroy");
status = pthread_mutex_destroy( &thelock->mut );
CHECK_STATUS("pthread_mutex_destroy");
PyMem_RawFree((void *)thelock);
}
PyLockStatus
PyThread_acquire_lock_timed(PyThread_type_lock lock, PY_TIMEOUT_T microseconds,
int intr_flag)
{
PyLockStatus success;
pthread_lock *thelock = (pthread_lock *)lock;
int status, error = 0;
dprintf(("PyThread_acquire_lock_timed(%p, %lld, %d) called\n",
lock, microseconds, intr_flag));
status = pthread_mutex_lock( &thelock->mut );
CHECK_STATUS("pthread_mutex_lock[1]");
if (thelock->locked == 0) {
success = PY_LOCK_ACQUIRED;
} else if (microseconds == 0) {
success = PY_LOCK_FAILURE;
} else {
struct timespec ts;
if (microseconds > 0)
MICROSECONDS_TO_TIMESPEC(microseconds, ts);
/* continue trying until we get the lock */
/* mut must be locked by me -- part of the condition
* protocol */
success = PY_LOCK_FAILURE;
while (success == PY_LOCK_FAILURE) {
if (microseconds > 0) {
status = pthread_cond_timedwait(
&thelock->lock_released,
&thelock->mut, &ts);
if (status == ETIMEDOUT)
break;
CHECK_STATUS("pthread_cond_timed_wait");
}
else {
status = pthread_cond_wait(
&thelock->lock_released,
&thelock->mut);
CHECK_STATUS("pthread_cond_wait");
}
if (intr_flag && status == 0 && thelock->locked) {
/* We were woken up, but didn't get the lock. We probably received
* a signal. Return PY_LOCK_INTR to allow the caller to handle
* it and retry. */
success = PY_LOCK_INTR;
break;
} else if (status == 0 && !thelock->locked) {
success = PY_LOCK_ACQUIRED;
} else {
success = PY_LOCK_FAILURE;
}
}
}
if (success == PY_LOCK_ACQUIRED) thelock->locked = 1;
status = pthread_mutex_unlock( &thelock->mut );
CHECK_STATUS("pthread_mutex_unlock[1]");
if (error) success = PY_LOCK_FAILURE;
dprintf(("PyThread_acquire_lock_timed(%p, %lld, %d) -> %d\n",
lock, microseconds, intr_flag, success));
return success;
}
void
PyThread_release_lock(PyThread_type_lock lock)
{
pthread_lock *thelock = (pthread_lock *)lock;
int status, error = 0;
(void) error; /* silence unused-but-set-variable warning */
dprintf(("PyThread_release_lock(%p) called\n", lock));
status = pthread_mutex_lock( &thelock->mut );
CHECK_STATUS("pthread_mutex_lock[3]");
thelock->locked = 0;
/* wake up someone (anyone, if any) waiting on the lock */
status = pthread_cond_signal( &thelock->lock_released );
CHECK_STATUS("pthread_cond_signal");
status = pthread_mutex_unlock( &thelock->mut );
CHECK_STATUS("pthread_mutex_unlock[3]");
}
#endif /* USE_SEMAPHORES */
int
PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
{
return PyThread_acquire_lock_timed(lock, waitflag ? -1 : 0, /*intr_flag=*/0);
}
/* set the thread stack size.
* Return 0 if size is valid, -1 if size is invalid,
* -2 if setting stack size is not supported.
*/
static int
_pythread_pthread_set_stacksize(size_t size)
{
#if defined(THREAD_STACK_SIZE)
pthread_attr_t attrs;
size_t tss_min;
int rc = 0;
#endif
/* set to default */
if (size == 0) {
_pythread_stacksize = 0;
return 0;
}
#if defined(THREAD_STACK_SIZE)
#if defined(PTHREAD_STACK_MIN)
tss_min = PTHREAD_STACK_MIN > THREAD_STACK_MIN ? PTHREAD_STACK_MIN
: THREAD_STACK_MIN;
#else
tss_min = THREAD_STACK_MIN;
#endif
if (size >= tss_min) {
/* validate stack size by setting thread attribute */
if (pthread_attr_init(&attrs) == 0) {
rc = pthread_attr_setstacksize(&attrs, size);
pthread_attr_destroy(&attrs);
if (rc == 0) {
_pythread_stacksize = size;
return 0;
}
}
}
return -1;
#else
return -2;
#endif
}
#define THREAD_SET_STACKSIZE(x) _pythread_pthread_set_stacksize(x)
#define Py_HAVE_NATIVE_TLS
int
PyThread_create_key(void)
{
pthread_key_t key;
int fail = pthread_key_create(&key, NULL);
return fail ? -1 : key;
}
void
PyThread_delete_key(int key)
{
pthread_key_delete(key);
}
void
PyThread_delete_key_value(int key)
{
pthread_setspecific(key, NULL);
}
int
PyThread_set_key_value(int key, void *value)
{
int fail;
fail = pthread_setspecific(key, value);
return fail ? -1 : 0;
}
void *
PyThread_get_key_value(int key)
{
return pthread_getspecific(key);
}
void
PyThread_ReInitTLS(void)
{}
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