Commit cdc95a0d93aa3b515f9c4fe30f47d52e8e7f3dde
2013-10-04T18:38:37
Use InterlockedCompareExchange for the lock
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diff --git a/src/global.c b/src/global.c
index fe3a3c8..33a760c 100644
--- a/src/global.c
+++ b/src/global.c
@@ -74,33 +74,12 @@ static void git__shutdown(void)
#if defined(GIT_THREADS) && defined(GIT_WIN32)
static DWORD _tls_index;
-static HANDLE _init_mutex = NULL;
-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 DWORD _mutex = 0;
static int synchronized_threads_init()
{
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();
if (git_mutex_init(&git__mwindow_mutex))
return -1;
@@ -110,56 +89,46 @@ static int synchronized_threads_init()
error = git_futils_dirs_global_init();
win32_pthread_initialize();
- SetEvent(_initialized_event);
- ReleaseMutex(_init_mutex);
+
return error;
}
int git_threads_init(void)
{
- int error = -1,
- n_inits = git_atomic_inc(&git__n_inits);
+ int error = 0;
+
+ /* Enter the lock */
+ while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
- if (n_inits == 1)
+ /* Only do work on a 0 -> 1 transition of the refcount */
+ if (1 == ++git__n_inits.val)
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;
}
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 */
git__shutdown();
TlsFree(_tls_index);
git_mutex_free(&git__mwindow_mutex);
-
- ReleaseMutex(_init_mutex);
}
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();
- GIT_MEMORY_BARRIER;
+
+ /* Exit the lock */
+ InterlockedExchange(&_mutex, 0);
}
git_global_st *git__global_state(void)