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/*

* Copyright (C) the libgit2 contributors. All rights reserved.

*

* 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 "filter.h"

#include "merge_driver.h"

#include "openssl_stream.h"

#include "thread-utils.h"

#include "git2/global.h"

#include "transports/ssh.h"

#if defined(GIT_MSVC_CRTDBG)

#include "win32/w32_stack.h"

#include "win32/w32_crtdbg_stacktrace.h"

#endif

git_mutex git__mwindow_mutex;

#define MAX_SHUTDOWN_CB 8

static git_global_shutdown_fn git__shutdown_callbacks[MAX_SHUTDOWN_CB];

static git_atomic git__n_shutdown_callbacks;

static git_atomic git__n_inits;

char *git__user_agent;

char *git__ssl_ciphers;

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__global_state_cleanup(git_global_st *st)

{

if (!st)

return;

git__free(st->error_t.message);

st->error_t.message = NULL;

}

static int init_common(void)

{

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 any other subsystems that have global state */

if ((ret = git_hash_global_init()) == 0 &&

(ret = git_sysdir_global_init()) == 0 &&

(ret = git_filter_global_init()) == 0 &&

(ret = git_merge_driver_global_init()) == 0 &&

(ret = git_transport_ssh_global_init()) == 0 &&

(ret = git_openssl_stream_global_init()) == 0)

ret = git_mwindow_global_init();

GIT_MEMORY_BARRIER;

return ret;

}

static void shutdown_common(void)

{

int pos;

/* Shutdown subsystems that have registered */

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();

}

git__free(git__user_agent);

git__free(git__ssl_ciphers);

}

/**

* Handle the global state with TLS

*

* If libgit2 is built with GIT_THREADS enabled,

* the `git_libgit2_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_libgit2_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_libgit2_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_libgit2_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();

git_threads_init();

if (git_mutex_init(&git__mwindow_mutex))

return -1;

error = init_common();

return error;

}

int git_libgit2_init(void)

{

int ret;

/* Enter the lock */

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

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

if ((ret = git_atomic_inc(&git__n_inits)) == 1) {

if (synchronized_threads_init() < 0)

ret = -1;

}

/* Exit the lock */

InterlockedExchange(&_mutex, 0);

return ret;

}

int git_libgit2_shutdown(void)

{

int ret;

/* Enter the lock */

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

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

if ((ret = git_atomic_dec(&git__n_inits)) == 0) {

shutdown_common();

git__free_tls_data();

TlsFree(_tls_index);

git_mutex_free(&git__mwindow_mutex);

#if defined(GIT_MSVC_CRTDBG)

git_win32__crtdbg_stacktrace_cleanup();

git_win32__stack_cleanup();

#endif

}

/* Exit the lock */

InterlockedExchange(&_mutex, 0);

return ret;

}

git_global_st *git__global_state(void)

{

git_global_st *ptr;

assert(git_atomic_get(&git__n_inits) > 0);

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

return ptr;

ptr = git__calloc(1, sizeof(git_global_st));

if (!ptr)

return NULL;

git_buf_init(&ptr->error_buf, 0);

TlsSetValue(_tls_index, ptr);

return ptr;

}

/**

* Free the TLS data associated with this thread.

* This should only be used by the thread as it

* is exiting.

*/

void git__free_tls_data(void)

{

void *ptr = TlsGetValue(_tls_index);

if (!ptr)

return;

git__global_state_cleanup(ptr);

git__free(ptr);

TlsSetValue(_tls_index, NULL);

}

BOOL WINAPI DllMain(HINSTANCE hInstDll, DWORD fdwReason, LPVOID lpvReserved)

{

GIT_UNUSED(hInstDll);

GIT_UNUSED(lpvReserved);

/* This is how Windows lets us know our thread is being shut down */

if (fdwReason == DLL_THREAD_DETACH) {

git__free_tls_data();

}

/*

* Windows pays attention to this during library loading. We don't do anything

* so we trivially succeed.

*/

return TRUE;

}

#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);

init_error = init_common();

}

int git_libgit2_init(void)

{

int ret, err;

ret = git_atomic_inc(&git__n_inits);

if ((err = pthread_mutex_lock(&_init_mutex)) != 0)

return err;

err = pthread_once(&_once_init, init_once);

err |= pthread_mutex_unlock(&_init_mutex);

if (err || init_error)

return err | init_error;

return ret;

}

int git_libgit2_shutdown(void)

{

void *ptr = NULL;

pthread_once_t new_once = PTHREAD_ONCE_INIT;

int ret;

if ((ret = git_atomic_dec(&git__n_inits)) != 0)

return ret;

if ((ret = pthread_mutex_lock(&_init_mutex)) != 0)

return ret;

/* 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_mutex_free(&git__mwindow_mutex);

_once_init = new_once;

if ((ret = pthread_mutex_unlock(&_init_mutex)) != 0)

return ret;

return 0;

}

git_global_st *git__global_state(void)

{

git_global_st *ptr;

assert(git_atomic_get(&git__n_inits) > 0);

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

return ptr;

}

#else

static git_global_st __state;

int git_libgit2_init(void)

{

int ret;

/* Only init subsystems the first time */

if ((ret = git_atomic_inc(&git__n_inits)) != 1)

return ret;

if ((ret = init_common()) < 0)

return ret;

return 1;

}

int git_libgit2_shutdown(void)

{

int ret;

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

if ((ret = git_atomic_dec(&git__n_inits)) == 0) {

shutdown_common();

git__global_state_cleanup(&__state);

memset(&__state, 0, sizeof(__state));

}

return ret;

}

git_global_st *git__global_state(void)

{

return &__state;

}

#endif /* GIT_THREADS */