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/*
* Copyright (C) 2009 Andrzej K. Haczewski <ahaczewski@gmail.com>
*
* DISCLAIMER: The implementation is Git-specific, it is subset of original
* Pthreads API, without lots of other features that Git doesn't use.
* Git also makes sure that the passed arguments are valid, so there's
* no need for double-checking.
*/
#include "../../git-compat-util.h"
#include "pthread.h"
#include <errno.h>
#include <limits.h>
static unsigned __stdcall win32_start_routine(void *arg)
{
pthread_t *thread = arg;
thread->arg = thread->start_routine(thread->arg);
return 0;
}
int pthread_create(pthread_t *thread, const void *unused,
void *(*start_routine)(void*), void *arg)
{
thread->arg = arg;
thread->start_routine = start_routine;
thread->handle = (HANDLE)
_beginthreadex(NULL, 0, win32_start_routine, thread, 0, NULL);
if (!thread->handle)
return errno;
else
return 0;
}
int win32_pthread_join(pthread_t *thread, void **value_ptr)
{
DWORD result = WaitForSingleObject(thread->handle, INFINITE);
switch (result) {
case WAIT_OBJECT_0:
if (value_ptr)
*value_ptr = thread->arg;
return 0;
case WAIT_ABANDONED:
return EINVAL;
default:
return err_win_to_posix(GetLastError());
}
}
int pthread_cond_init(pthread_cond_t *cond, const void *unused)
{
cond->waiters = 0;
cond->was_broadcast = 0;
InitializeCriticalSection(&cond->waiters_lock);
cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
if (!cond->sema)
die("CreateSemaphore() failed");
cond->continue_broadcast = CreateEvent(NULL, /* security */
FALSE, /* auto-reset */
FALSE, /* not signaled */
NULL); /* name */
if (!cond->continue_broadcast)
die("CreateEvent() failed");
return 0;
}
int pthread_cond_destroy(pthread_cond_t *cond)
{
CloseHandle(cond->sema);
CloseHandle(cond->continue_broadcast);
DeleteCriticalSection(&cond->waiters_lock);
return 0;
}
int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex)
{
int last_waiter;
EnterCriticalSection(&cond->waiters_lock);
cond->waiters++;
LeaveCriticalSection(&cond->waiters_lock);
/*
* Unlock external mutex and wait for signal.
* NOTE: we've held mutex locked long enough to increment
* waiters count above, so there's no problem with
* leaving mutex unlocked before we wait on semaphore.
*/
LeaveCriticalSection(mutex);
/* let's wait - ignore return value */
WaitForSingleObject(cond->sema, INFINITE);
/*
* Decrease waiters count. If we are the last waiter, then we must
* notify the broadcasting thread that it can continue.
* But if we continued due to cond_signal, we do not have to do that
* because the signaling thread knows that only one waiter continued.
*/
EnterCriticalSection(&cond->waiters_lock);
cond->waiters--;
last_waiter = cond->was_broadcast && cond->waiters == 0;
LeaveCriticalSection(&cond->waiters_lock);
if (last_waiter) {
/*
* cond_broadcast was issued while mutex was held. This means
* that all other waiters have continued, but are contending
* for the mutex at the end of this function because the
* broadcasting thread did not leave cond_broadcast, yet.
* (This is so that it can be sure that each waiter has
* consumed exactly one slice of the semaphor.)
* The last waiter must tell the broadcasting thread that it
* can go on.
*/
SetEvent(cond->continue_broadcast);
/*
* Now we go on to contend with all other waiters for
* the mutex. Auf in den Kampf!
*/
}
/* lock external mutex again */
EnterCriticalSection(mutex);
return 0;
}
/*
* IMPORTANT: This implementation requires that pthread_cond_signal
* is called while the mutex is held that is used in the corresponding
* pthread_cond_wait calls!
*/
int pthread_cond_signal(pthread_cond_t *cond)
{
int have_waiters;
EnterCriticalSection(&cond->waiters_lock);
have_waiters = cond->waiters > 0;
LeaveCriticalSection(&cond->waiters_lock);
/*
* Signal only when there are waiters
*/
if (have_waiters)
return ReleaseSemaphore(cond->sema, 1, NULL) ?
0 : err_win_to_posix(GetLastError());
else
return 0;
}
/*
* DOUBLY IMPORTANT: This implementation requires that pthread_cond_broadcast
* is called while the mutex is held that is used in the corresponding
* pthread_cond_wait calls!
*/
int pthread_cond_broadcast(pthread_cond_t *cond)
{
EnterCriticalSection(&cond->waiters_lock);
if ((cond->was_broadcast = cond->waiters > 0)) {
/* wake up all waiters */
ReleaseSemaphore(cond->sema, cond->waiters, NULL);
LeaveCriticalSection(&cond->waiters_lock);
/*
* At this point all waiters continue. Each one takes its
* slice of the semaphor. Now it's our turn to wait: Since
* the external mutex is held, no thread can leave cond_wait,
* yet. For this reason, we can be sure that no thread gets
* a chance to eat *more* than one slice. OTOH, it means
* that the last waiter must send us a wake-up.
*/
WaitForSingleObject(cond->continue_broadcast, INFINITE);
/*
* Since the external mutex is held, no thread can enter
* cond_wait, and, hence, it is safe to reset this flag
* without cond->waiters_lock held.
*/
cond->was_broadcast = 0;
} else {
LeaveCriticalSection(&cond->waiters_lock);
}
return 0;
}
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