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Build generic internal library interface for thread local storage #5602

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Build generic internal library interface for thread local storage #5602

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d0ac8ee
Implement generic TLS interface
implausible Aug 6, 2020
0a69763
Replace global storage TLS with new interface
implausible Aug 6, 2020
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62 changes: 28 additions & 34 deletions src/global.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,6 @@ git_mutex git__mwindow_mutex;
typedef int (*git_global_init_fn)(void);

static git_global_init_fn git__init_callbacks[] = {
git_allocator_global_init,
git_hash_global_init,
git_sysdir_global_init,
git_filter_global_init,
Expand Down Expand Up @@ -69,12 +68,6 @@ static int init_common(void)
size_t i;
int ret;

/* Initialize the CRT debug allocator first, before our first malloc */
#if defined(GIT_MSVC_CRTDBG)
git_win32__crtdbg_stacktrace_init();
git_win32__stack_init();
#endif

/* Initialize subsystems that have global state */
for (i = 0; i < ARRAY_SIZE(git__init_callbacks); i++)
if ((ret = git__init_callbacks[i]()) != 0)
Expand Down Expand Up @@ -139,22 +132,34 @@ static void shutdown_common(void)
* before cache invalidation of the subsystems' newly written global
* state.
*/
#if defined(GIT_THREADS) && defined(GIT_WIN32)

static DWORD _fls_index;
static volatile LONG _mutex = 0;
#if defined(GIT_THREADS)
static git_tls_data *_tls_data = NULL;

static void WINAPI fls_free(void *st)
static void tls_free(void *st)
{
git__global_state_cleanup(st);
git__free(st);
}
#endif

#if defined(GIT_THREADS) && defined(GIT_WIN32)

static volatile LONG _mutex = 0;

static int synchronized_threads_init(void)
{
int error;

if ((_fls_index = FlsAlloc(fls_free)) == FLS_OUT_OF_INDEXES)
git_allocator_global_init();

/* Initialize the CRT debug allocator first, before our first malloc */
#if defined(GIT_MSVC_CRTDBG)
git_win32__crtdbg_stacktrace_init();
git_win32__stack_init();
#endif

if (git_tls_data__init(&_tls_data, &tls_free) < 0)
return -1;

git_threads_init();
Expand Down Expand Up @@ -197,7 +202,8 @@ int git_libgit2_shutdown(void)
if ((ret = git_atomic_dec(&git__n_inits)) == 0) {
shutdown_common();

FlsFree(_fls_index);
git_tls_data__free(_tls_data);
_tls_data = NULL;
git_mutex_free(&git__mwindow_mutex);

#if defined(GIT_MSVC_CRTDBG)
Expand All @@ -218,7 +224,7 @@ git_global_st *git__global_state(void)

assert(git_atomic_get(&git__n_inits) > 0);

if ((ptr = FlsGetValue(_fls_index)) != NULL)
if ((ptr = git_tls_data__get(_tls_data)) != NULL)
return ptr;

ptr = git__calloc(1, sizeof(git_global_st));
Expand All @@ -227,30 +233,23 @@ git_global_st *git__global_state(void)

git_buf_init(&ptr->error_buf, 0);

FlsSetValue(_fls_index, ptr);
git_tls_data__set(_tls_data, ptr);
return ptr;
}

#elif defined(GIT_THREADS) && defined(_POSIX_THREADS)

static pthread_key_t _tls_key;
static pthread_mutex_t _init_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_once_t _once_init = PTHREAD_ONCE_INIT;
int init_error = 0;

static void cb__free_status(void *st)
{
git__global_state_cleanup(st);
git__free(st);
}

static void init_once(void)
{
if ((init_error = git_mutex_init(&git__mwindow_mutex)) != 0)
return;

pthread_key_create(&_tls_key, &cb__free_status);

git_allocator_global_init();
git_tls_data__init(&_tls_data, &tls_free);
init_error = init_common();
}

Expand All @@ -273,7 +272,6 @@ int git_libgit2_init(void)

int git_libgit2_shutdown(void)
{
void *ptr = NULL;
pthread_once_t new_once = PTHREAD_ONCE_INIT;
int error, ret;

Expand All @@ -286,13 +284,8 @@ int git_libgit2_shutdown(void)
/* Shut down any subsystems that have global state */
shutdown_common();

ptr = pthread_getspecific(_tls_key);
pthread_setspecific(_tls_key, NULL);

git__global_state_cleanup(ptr);
git__free(ptr);

pthread_key_delete(_tls_key);
git_tls_data__free(_tls_data);
_tls_data = NULL;
git_mutex_free(&git__mwindow_mutex);
_once_init = new_once;

Expand All @@ -309,15 +302,15 @@ git_global_st *git__global_state(void)

assert(git_atomic_get(&git__n_inits) > 0);

if ((ptr = pthread_getspecific(_tls_key)) != NULL)
if ((ptr = git_tls_data__get(_tls_data)) != NULL)
return ptr;

ptr = git__calloc(1, sizeof(git_global_st));
if (!ptr)
return NULL;

git_buf_init(&ptr->error_buf, 0);
pthread_setspecific(_tls_key, ptr);
git_tls_data__set(_tls_data, ptr);
return ptr;
}

Expand All @@ -333,6 +326,7 @@ int git_libgit2_init(void)
if ((ret = git_atomic_inc(&git__n_inits)) != 1)
return ret;

git_allocator_global_init();
if ((ret = init_common()) < 0)
return ret;

Expand Down
205 changes: 205 additions & 0 deletions src/thread-utils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -56,3 +56,208 @@ int git_online_cpus(void)

return 1;
}

#ifndef GIT_THREADS

struct git_tls_data {
void GIT_CALLBACK(free_fn)(void *payload);
void *storage;
};

int git_tls_data__init(git_tls_data **out,
void GIT_CALLBACK(free_fn)(void *storage))
{
struct git_tls_data *tls = git__malloc(sizeof(struct git_tls_data));
GIT_ERROR_CHECK_ALLOC(tls);

tls->storage = NULL;
tls->free_fn = free_fn;
*out = tls;

return 0;
}

int git_tls_data__set(git_tls_data *tls, void *payload)
{
tls->storage = payload;
return 0;
}

void *git_tls_data__get(git_tls_data *tls)
{
return tls->storage;
}

void git_tls_data__free(git_tls_data *tls)
{
tls->free_fn(tls->storage);
git__free(tls);
}

#elif defined(GIT_WIN32)

struct git_tls_data {
void GIT_CALLBACK(free_fn)(void *payload);
DWORD fls_index;
};

struct git_tls_cell {
void GIT_CALLBACK(free_fn)(void *storage);
void *storage;
};

static void WINAPI git_tls_cell__free(void *sc)
{
struct git_tls_cell *storage_cell = sc;
if (storage_cell == NULL) {
return;
}

storage_cell->free_fn(storage_cell->storage);
git__free(storage_cell);
}

int git_tls_data__init(git_tls_data **out,
void GIT_CALLBACK(free_fn)(void *payload))
{
struct git_tls_data *tls = git__malloc(sizeof(struct git_tls_data));
GIT_ERROR_CHECK_ALLOC(tls);

if ((tls->fls_index = FlsAlloc(git_tls_cell__free)) == FLS_OUT_OF_INDEXES) {
git__free(tls);
return -1;
}

tls->free_fn = free_fn;
*out = tls;

return 0;
}

int git_tls_data__set(git_tls_data *tls, void *payload)
{
struct git_tls_cell *storage_cell;

if (payload == NULL) {
if ((storage_cell = FlsGetValue(tls->fls_index)) != NULL)
git_tls_cell__free(storage_cell);

if (FlsSetValue(tls->fls_index, NULL) == 0)
return -1;

return 0;
}

storage_cell = git__malloc(sizeof(struct git_tls_cell));
GIT_ERROR_CHECK_ALLOC(storage_cell);

storage_cell->free_fn = tls->free_fn;
storage_cell->storage = payload;

if (FlsSetValue(tls->fls_index, storage_cell) == 0) {
git__free(storage_cell);
return -1;
}

return 0;
}

void *git_tls_data__get(git_tls_data *tls)
{
struct git_tls_cell *storage_cell = FlsGetValue(tls->fls_index);
if (storage_cell == NULL)
return NULL;

return storage_cell->storage;
}

void git_tls_data__free(git_tls_data *tls)
{
FlsFree(tls->fls_index);
tls->free_fn = NULL;
git__free(tls);
}

#elif defined(_POSIX_THREADS)

struct git_tls_data {
void GIT_CALLBACK(free_fn)(void *payload);
pthread_key_t tls_key;
};

struct git_tls_cell {
void GIT_CALLBACK(free_fn)(void *storage);
void *storage;
};

static void git_tls_cell__free(void *sc)
{
struct git_tls_cell *storage_cell = sc;
storage_cell->free_fn(storage_cell->storage);
git__free(storage_cell);
}

int git_tls_data__init(git_tls_data **out,
void GIT_CALLBACK(free_fn)(void *payload))
{
struct git_tls_data *tls = git__malloc(sizeof(struct git_tls_data));
GIT_ERROR_CHECK_ALLOC(tls);

if (pthread_key_create(&tls->tls_key, git_tls_cell__free) != 0) {
git__free(tls);
return -1;
}

tls->free_fn = free_fn;
*out = tls;

return 0;
}

int git_tls_data__set(git_tls_data *tls, void *payload)
{
struct git_tls_cell *storage_cell;

if (payload == NULL) {
if ((storage_cell = pthread_getspecific(tls->tls_key)) != NULL)
git_tls_cell__free(storage_cell);

if (pthread_setspecific(tls->tls_key, NULL) != 0)
return -1;

return 0;
}

storage_cell = git__malloc(sizeof(struct git_tls_cell));
GIT_ERROR_CHECK_ALLOC(storage_cell);

storage_cell->free_fn = tls->free_fn;
storage_cell->storage = payload;

if (pthread_setspecific(tls->tls_key, storage_cell) != 0) {
git__free(storage_cell);
return -1;
}

return 0;
}

void *git_tls_data__get(git_tls_data *tls)
{
struct git_tls_cell *storage_cell = pthread_getspecific(tls->tls_key);
if (storage_cell == NULL)
return NULL;

return storage_cell->storage;
}

void git_tls_data__free(git_tls_data *tls)
{
git_tls_data__set(tls, NULL);
pthread_key_delete(tls->tls_key);
git__free(tls);
}

#else
# error unknown threading model
#endif
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