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Use InterlockedCompareExchange for the lock

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This commit is contained in:
Philip Kelley 2013-10-04 18:38:37 -04:00 committed by Ben Straub
parent e411b74ebd
commit cdc95a0d93
1 changed files with 18 additions and 49 deletions
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67
src/global.c
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@ -74,33 +74,12 @@ static void git__shutdown(void)
#if defined(GIT_THREADS) && defined(GIT_WIN32) #if defined(GIT_THREADS) && defined(GIT_WIN32)
static DWORD _tls_index; static DWORD _tls_index;
static HANDLE _init_mutex = NULL; static DWORD _mutex = 0;
static HANDLE _initialized_event = NULL;
static int synchronized_init_and_claim_mutex(volatile HANDLE *m)
{
if (*m == NULL) {
HANDLE nm = CreateMutex(NULL, FALSE, NULL);
if (InterlockedCompareExchangePointer(m, nm, NULL) != NULL) {
CloseHandle(nm);
}
}
return WaitForSingleObject(*m, INFINITE) == WAIT_FAILED;
}
static int synchronized_threads_init() static int synchronized_threads_init()
{ {
int error; int error;
if (synchronized_init_and_claim_mutex(&_init_mutex) != WAIT_OBJECT_0) {
giterr_set(GITERR_OS, "git_threads_init: WaitForSingleObject failed");
return -1;
}
if (!_initialized_event) {
_initialized_event = CreateEvent(NULL, TRUE, FALSE, NULL);
}
_tls_index = TlsAlloc(); _tls_index = TlsAlloc();
if (git_mutex_init(&git__mwindow_mutex)) if (git_mutex_init(&git__mwindow_mutex))
return -1; return -1;
@ -110,56 +89,46 @@ static int synchronized_threads_init()
error = git_futils_dirs_global_init(); error = git_futils_dirs_global_init();
win32_pthread_initialize(); win32_pthread_initialize();
SetEvent(_initialized_event);
ReleaseMutex(_init_mutex);
return error; return error;
} }
int git_threads_init(void) int git_threads_init(void)
{ {
int error = -1, int error = 0;
n_inits = git_atomic_inc(&git__n_inits);
if (n_inits == 1) /* Enter the lock */
while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
/* Only do work on a 0 -> 1 transition of the refcount */
if (1 == ++git__n_inits.val)
error = synchronized_threads_init(); error = synchronized_threads_init();
else {
while (!_initialized_event); /* SPIN */
error = (WaitForSingleObject(_initialized_event, INFINITE) == WAIT_OBJECT_0) ? 0 : -1;
}
GIT_MEMORY_BARRIER; /* Exit the lock */
InterlockedExchange(&_mutex, 0);
return error; return error;
} }
static void synchronized_threads_shutdown() static void synchronized_threads_shutdown()
{ {
if (WaitForSingleObject(_init_mutex, INFINITE) != WAIT_OBJECT_0) {
giterr_set(GITERR_OS, "git_threads_shutdown: WaitForSingleObject failed");
return;
}
if (git__n_inits.val != 0) {
/* Someone else initialized while we were waiting */
ReleaseMutex(_init_mutex);
return;
}
ResetEvent(_initialized_event);
/* Shut down any subsystems that have global state */ /* Shut down any subsystems that have global state */
git__shutdown(); git__shutdown();
TlsFree(_tls_index); TlsFree(_tls_index);
git_mutex_free(&git__mwindow_mutex); git_mutex_free(&git__mwindow_mutex);
ReleaseMutex(_init_mutex);
} }
void git_threads_shutdown(void) void git_threads_shutdown(void)
{ {
int n_inits = git_atomic_dec(&git__n_inits); /* Enter the lock */
while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
if (n_inits == 0) /* Only do work on a 1 -> 0 transition of the refcount */
if (0 == --git__n_inits.val)
synchronized_threads_shutdown(); synchronized_threads_shutdown();
GIT_MEMORY_BARRIER;
/* Exit the lock */
InterlockedExchange(&_mutex, 0);
} }
git_global_st *git__global_state(void) git_global_st *git__global_state(void)