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* This file is part of libgit2, distributed under the GNU GPL v2 with

* a Linking Exception. For full terms see the included COPYING file.

#include "common.h"

#include "global.h"

#include "hash.h"

#include "sysdir.h"

#include "git2/threads.h"

#include "thread-utils.h"

git_mutex git__mwindow_mutex;

#define MAX_SHUTDOWN_CB 8

#ifdef GIT_SSL

# include <openssl/ssl.h>

SSL_CTX *git__ssl_ctx;

# ifdef GIT_THREADS

static git_mutex *openssl_locks;

# endif

#endif

static git_global_shutdown_fn git__shutdown_callbacks[MAX_SHUTDOWN_CB];

static git_atomic git__n_shutdown_callbacks;

static git_atomic git__n_inits;

void git__on_shutdown(git_global_shutdown_fn callback)

{

int count = git_atomic_inc(&git__n_shutdown_callbacks);

assert(count <= MAX_SHUTDOWN_CB && count > 0);

git__shutdown_callbacks[count - 1] = callback;

}

static void git__shutdown(void)

{

int pos;

for (pos = git_atomic_get(&git__n_shutdown_callbacks); pos > 0; pos = git_atomic_dec(&git__n_shutdown_callbacks)) {

git_global_shutdown_fn cb = git__swap(git__shutdown_callbacks[pos - 1], NULL);

if (cb != NULL)

cb();

}

#if defined(GIT_THREADS) && defined(GIT_SSL)

void openssl_locking_function(int mode, int n, const char *file, int line)

{

int lock;

GIT_UNUSED(file);

GIT_UNUSED(line);

lock = mode & CRYPTO_LOCK;

if (lock) {

git_mutex_lock(&openssl_locks[n]);

} else {

git_mutex_unlock(&openssl_locks[n]);

}

#endif

static void init_ssl(void)

{

#ifdef GIT_SSL

SSL_load_error_strings();

OpenSSL_add_ssl_algorithms();

git__ssl_ctx = SSL_CTX_new(SSLv23_method());

SSL_CTX_set_mode(git__ssl_ctx, SSL_MODE_AUTO_RETRY);

SSL_CTX_set_verify(git__ssl_ctx, SSL_VERIFY_NONE, NULL);

if (!SSL_CTX_set_default_verify_paths(git__ssl_ctx)) {

SSL_CTX_free(git__ssl_ctx);

git__ssl_ctx = NULL;

}

# ifdef GIT_THREADS

{

int num_locks, i;

num_locks = CRYPTO_num_locks();

openssl_locks = git__calloc(num_locks, sizeof(git_mutex));

if (openssl_locks == NULL) {

SSL_CTX_free(git__ssl_ctx);

git__ssl_ctx = NULL;

}

for (i = 0; i < num_locks; i++) {

if (git_mutex_init(&openssl_locks[i]) != 0) {

SSL_CTX_free(git__ssl_ctx);

git__ssl_ctx = NULL;

}

CRYPTO_set_locking_callback(openssl_locking_function);

}

# endif

#endif

}

/**

* Handle the global state with TLS

* If libgit2 is built with GIT_THREADS enabled,

* the `git_threads_init()` function must be called

* before calling any other function of the library.

* This function allocates a TLS index (using pthreads

* or the native Win32 API) to store the global state

* on a per-thread basis.

* Any internal method that requires global state will

* then call `git__global_state()` which returns a pointer

* to the global state structure; this pointer is lazily

* allocated on each thread.

* Before shutting down the library, the

* `git_threads_shutdown` method must be called to free

* the previously reserved TLS index.

* If libgit2 is built without threading support, the

* `git__global_statestate()` call returns a pointer to a single,

* statically allocated global state. The `git_thread_`

* functions are not available in that case.

* `git_threads_init()` allows subsystems to perform global setup,

* which may take place in the global scope. An explicit memory

* fence exists at the exit of `git_threads_init()`. Without this,

* CPU cores are free to reorder cache invalidation of `_tls_init`

* before cache invalidation of the subsystems' newly written global

* state.

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

static DWORD _tls_index;

static volatile LONG _mutex = 0;

static int synchronized_threads_init(void)

{

int error;

_tls_index = TlsAlloc();

if (git_mutex_init(&git__mwindow_mutex))

return -1;

/* Initialize any other subsystems that have global state */

if ((error = git_hash_global_init()) >= 0)

error = git_sysdir_global_init();

win32_pthread_initialize();

return error;

}

int git_threads_init(void)

{

int error = 0;

/* Enter the lock */

while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }

/* Only do work on a 0 -> 1 transition of the refcount */

if (1 == git_atomic_inc(&git__n_inits))

error = synchronized_threads_init();

/* Exit the lock */

InterlockedExchange(&_mutex, 0);

return error;

}

static void synchronized_threads_shutdown(void)

{

/* Shut down any subsystems that have global state */

git__shutdown();

TlsFree(_tls_index);

git_mutex_free(&git__mwindow_mutex);

}

void git_threads_shutdown(void)

{

/* Enter the lock */

while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }

/* Only do work on a 1 -> 0 transition of the refcount */

if (0 == git_atomic_dec(&git__n_inits))

synchronized_threads_shutdown();

/* Exit the lock */

InterlockedExchange(&_mutex, 0);

}

git_global_st *git__global_state(void)

{

void *ptr;

assert(git_atomic_get(&git__n_inits) > 0);

if ((ptr = TlsGetValue(_tls_index)) != NULL)

return ptr;

ptr = git__malloc(sizeof(git_global_st));

if (!ptr)

return NULL;

memset(ptr, 0x0, sizeof(git_global_st));

TlsSetValue(_tls_index, ptr);

return ptr;

}

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

static pthread_key_t _tls_key;

static pthread_once_t _once_init = PTHREAD_ONCE_INIT;

int init_error = 0;

static void cb__free_status(void *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);

/* Initialize any other subsystems that have global state */

if ((init_error = git_hash_global_init()) >= 0)

init_error = git_sysdir_global_init();

/* OpenSSL needs to be initialized from the main thread */

init_ssl();

GIT_MEMORY_BARRIER;

}

int git_threads_init(void)

{

pthread_once(&_once_init, init_once);

git_atomic_inc(&git__n_inits);

return init_error;

}

void git_threads_shutdown(void)

{

void *ptr = NULL;

pthread_once_t new_once = PTHREAD_ONCE_INIT;

if (git_atomic_dec(&git__n_inits) > 0) return;

/* Shut down any subsystems that have global state */

git__shutdown();

ptr = pthread_getspecific(_tls_key);

pthread_setspecific(_tls_key, NULL);

git__free(ptr);

pthread_key_delete(_tls_key);

git_mutex_free(&git__mwindow_mutex);

_once_init = new_once;

}

git_global_st *git__global_state(void)

{

void *ptr;

assert(git_atomic_get(&git__n_inits) > 0);

if ((ptr = pthread_getspecific(_tls_key)) != NULL)

return ptr;

ptr = git__malloc(sizeof(git_global_st));

if (!ptr)

return NULL;

memset(ptr, 0x0, sizeof(git_global_st));

pthread_setspecific(_tls_key, ptr);

return ptr;

}

#else

static git_global_st __state;

int git_threads_init(void)

{

static int ssl_inited = 0;

if (!ssl_inited) {

init_ssl();

ssl_inited = 1;

}

git_atomic_inc(&git__n_inits);

return 0;

}

void git_threads_shutdown(void)

{

/* Shut down any subsystems that have global state */

if (0 == git_atomic_dec(&git__n_inits))

git__shutdown();

}

git_global_st *git__global_state(void)

{

return &__state;

}

#endif /* GIT_THREADS */

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