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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 "fileops.h"

#include "git2/threads.h"

#include "thread-utils.h"

git_mutex git__mwindow_mutex;

/**

* 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 int _tls_init = 0;

int git_threads_init(void)

{

int error;

if (_tls_init)

return 0;

_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_futils_dirs_global_init()) >= 0)

_tls_init = 1;

GIT_MEMORY_BARRIER;

return error;

}

void git_threads_shutdown(void)

{

TlsFree(_tls_index);

_tls_init = 0;

git_mutex_free(&git__mwindow_mutex);

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

git_hash_global_shutdown();

git_futils_dirs_free();

}

git_global_st *git__global_state(void)

{

void *ptr;

assert(_tls_init);

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 int _tls_init = 0;

static void cb__free_status(void *st)

{

git__free(st);

}

int git_threads_init(void)

{

int error = 0;

if (_tls_init)

return 0;

if (git_mutex_init(&git__mwindow_mutex))

return -1;

pthread_key_create(&_tls_key, &cb__free_status);

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

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

(error = git_futils_dirs_global_init()) >= 0)

_tls_init = 1;

GIT_MEMORY_BARRIER;

return error;

}

void git_threads_shutdown(void)

{

if (_tls_init) {

void *ptr = pthread_getspecific(_tls_key);

pthread_setspecific(_tls_key, NULL);

git__free(ptr);

}

pthread_key_delete(_tls_key);

_tls_init = 0;

git_mutex_free(&git__mwindow_mutex);

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

git_hash_global_shutdown();

git_futils_dirs_free();

}

git_global_st *git__global_state(void)

{

void *ptr;

assert(_tls_init);

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)

{

/* noop */

return 0;

}

void git_threads_shutdown(void)

{

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

git_hash_global_shutdown();

git_futils_dirs_free();

}

git_global_st *git__global_state(void)

{

return &__state;

}

#endif /* GIT_THREADS */