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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 "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();
git_mutex_init(&git__mwindow_mutex);
/* Initialize any other subsystems that have global state */
if ((error = git_hash_global_init()) >= 0)
_tls_init = 1;
if (error == 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_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;
git_mutex_init(&git__mwindow_mutex);
pthread_key_create(&_tls_key, &cb__free_status);
/* Initialize any other subsystems that have global state */
if ((error = git_hash_global_init()) >= 0)
_tls_init = 1;
GIT_MEMORY_BARRIER;
return error;
}
void git_threads_shutdown(void)
{
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_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)
{
/* noop */
}
git_global_st *git__global_state(void)
{
return &__state;
}
#endif /* GIT_THREADS */
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