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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 "global.h"
#include "alloc.h"
#include "threadstate.h"
#include "hash.h"
#include "sysdir.h"
#include "filter.h"
#include "settings.h"
#include "mwindow.h"
#include "merge_driver.h"
#include "pool.h"
#include "streams/registry.h"
#include "streams/mbedtls.h"
#include "streams/openssl.h"
#include "thread-utils.h"
#include "git2/global.h"
#include "transports/ssh.h"
#include "win32/w32_stack.h"
typedef int (*git_global_init_fn)(void);
static git_global_init_fn git__init_callbacks[] = {
git_allocator_global_init,
git_threadstate_global_init,
git_threads_global_init,
git_hash_global_init,
git_sysdir_global_init,
git_filter_global_init,
git_merge_driver_global_init,
git_transport_ssh_global_init,
git_stream_registry_global_init,
git_openssl_stream_global_init,
git_mbedtls_stream_global_init,
git_mwindow_global_init,
git_pool_global_init,
git_settings_global_init
};
static git_global_shutdown_fn git__shutdown_callbacks[ARRAY_SIZE(git__init_callbacks)];
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 <= (int) ARRAY_SIZE(git__shutdown_callbacks) && count > 0);
git__shutdown_callbacks[count - 1] = callback;
}
static int init_common(void)
{
size_t i;
int ret;
/* Initialize subsystems that have global state */
for (i = 0; i < ARRAY_SIZE(git__init_callbacks); i++)
if ((ret = git__init_callbacks[i]()) != 0)
break;
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_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)
/*
* On Win32, we use a spinlock to provide locking semantics. This is
* lighter-weight than a proper critical section.
*/
static volatile LONG init_spinlock = 0;
GIT_INLINE(int) init_lock(void)
{
while (InterlockedCompareExchange(&init_spinlock, 1, 0)) { Sleep(0); }
return 0;
}
GIT_INLINE(int) init_unlock(void)
{
InterlockedExchange(&init_spinlock, 0);
return 0;
}
#elif defined(GIT_THREADS) && defined(_POSIX_THREADS)
/*
* On POSIX, we need to use a proper mutex for locking. We might prefer
* a spinlock here, too, but there's no static initializer for a
* pthread_spinlock_t.
*/
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
GIT_INLINE(int) init_lock(void)
{
return pthread_mutex_lock(&mutex) == 0 ? 0 : -1;
}
GIT_INLINE(int) init_unlock(void)
{
return pthread_mutex_unlock(&mutex) == 0 ? 0 : -1;
}
#elif defined(GIT_THREADS)
# error unknown threading model
#else
# define init_lock() 0
# define init_unlock() 0
#endif
int git_libgit2_init(void)
{
int ret;
if (init_lock() < 0)
return -1;
/* Only do work on a 0 -> 1 transition of the refcount */
if ((ret = git_atomic_inc(&git__n_inits)) == 1) {
if (init_common() < 0)
ret = -1;
}
if (init_unlock() < 0)
return -1;
return ret;
}
int git_libgit2_shutdown(void)
{
int ret;
/* Enter the lock */
if (init_lock() < 0)
return -1;
/* Only do work on a 1 -> 0 transition of the refcount */
if ((ret = git_atomic_dec(&git__n_inits)) == 0)
shutdown_common();
/* Exit the lock */
if (init_unlock() < 0)
return -1;
return ret;
}
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