thodg/libgit2

diff --git a/src/errors.c b/src/errors.c
index 8570226..d4da50d 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -7,7 +7,7 @@
 
 #include "common.h"
 
-#include "global.h"
+#include "threadstate.h"
 #include "posix.h"
 #include "buffer.h"
 
@@ -22,18 +22,18 @@ static git_error g_git_oom_error = {
 
 static void set_error_from_buffer(int error_class)
 {
-	git_error *error = &GIT_GLOBAL->error_t;
-	git_buf *buf = &GIT_GLOBAL->error_buf;
+	git_error *error = &GIT_THREADSTATE->error_t;
+	git_buf *buf = &GIT_THREADSTATE->error_buf;
 
 	error->message = buf->ptr;
 	error->klass = error_class;
 
-	GIT_GLOBAL->last_error = error;
+	GIT_THREADSTATE->last_error = error;
 }
 
 static void set_error(int error_class, char *string)
 {
-	git_buf *buf = &GIT_GLOBAL->error_buf;
+	git_buf *buf = &GIT_THREADSTATE->error_buf;
 
 	git_buf_clear(buf);
 	if (string) {
@@ -46,7 +46,7 @@ static void set_error(int error_class, char *string)
 
 void git_error_set_oom(void)
 {
-	GIT_GLOBAL->last_error = &g_git_oom_error;
+	GIT_THREADSTATE->last_error = &g_git_oom_error;
 }
 
 void git_error_set(int error_class, const char *fmt, ...)
@@ -64,7 +64,7 @@ void git_error_vset(int error_class, const char *fmt, va_list ap)
 	DWORD win32_error_code = (error_class == GIT_ERROR_OS) ? GetLastError() : 0;
 #endif
 	int error_code = (error_class == GIT_ERROR_OS) ? errno : 0;
-	git_buf *buf = &GIT_GLOBAL->error_buf;
+	git_buf *buf = &GIT_THREADSTATE->error_buf;
 
 	git_buf_clear(buf);
 	if (fmt) {
@@ -97,7 +97,7 @@ void git_error_vset(int error_class, const char *fmt, va_list ap)
 
 int git_error_set_str(int error_class, const char *string)
 {
-	git_buf *buf = &GIT_GLOBAL->error_buf;
+	git_buf *buf = &GIT_THREADSTATE->error_buf;
 
 	assert(string);
 
@@ -118,9 +118,9 @@ int git_error_set_str(int error_class, const char *string)
 
 void git_error_clear(void)
 {
-	if (GIT_GLOBAL->last_error != NULL) {
+	if (GIT_THREADSTATE->last_error != NULL) {
 		set_error(0, NULL);
-		GIT_GLOBAL->last_error = NULL;
+		GIT_THREADSTATE->last_error = NULL;
 	}
 
 	errno = 0;
@@ -131,13 +131,13 @@ void git_error_clear(void)
 
 const git_error *git_error_last(void)
 {
-	return GIT_GLOBAL->last_error;
+	return GIT_THREADSTATE->last_error;
 }
 
 int git_error_state_capture(git_error_state *state, int error_code)
 {
-	git_error *error = GIT_GLOBAL->last_error;
-	git_buf *error_buf = &GIT_GLOBAL->error_buf;
+	git_error *error = GIT_THREADSTATE->last_error;
+	git_buf *error_buf = &GIT_THREADSTATE->error_buf;
 
 	memset(state, 0, sizeof(git_error_state));
 
diff --git a/src/global.c b/src/global.c
index f67811a..c4e925b 100644
--- a/src/global.c
+++ b/src/global.c
@@ -8,6 +8,7 @@
 #include "global.h"
 
 #include "alloc.h"
+#include "threadstate.h"
 #include "hash.h"
 #include "sysdir.h"
 #include "filter.h"
@@ -27,6 +28,7 @@ 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,
@@ -53,15 +55,6 @@ void git__on_shutdown(git_global_shutdown_fn callback)
 	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)
 {
 	size_t i;
@@ -94,32 +87,6 @@ static void shutdown_common(void)
 	}
 }
 
-/**
- * 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
@@ -130,42 +97,67 @@ static void shutdown_common(void)
  */
 #if defined(GIT_THREADS) && defined(GIT_WIN32)
 
-static DWORD _fls_index;
-static volatile LONG _mutex = 0;
+/*
+ * 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;
 
-static void WINAPI fls_free(void *st)
+GIT_INLINE(int) init_lock(void)
 {
-	git__global_state_cleanup(st);
-	git__free(st);
+	while (InterlockedCompareExchange(&init_spinlock, 1, 0)) { Sleep(0); }
+	return 0;
 }
 
-static int synchronized_threads_init(void)
+GIT_INLINE(int) init_unlock(void)
 {
-	int error;
+	InterlockedExchange(&init_spinlock, 0);
+	return 0;
+}
 
-	if ((_fls_index = FlsAlloc(fls_free)) == FLS_OUT_OF_INDEXES)
-		return -1;
+#elif defined(GIT_THREADS) && defined(_POSIX_THREADS)
 
-	error = init_common();
+/*
+ * 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;
 
-	return error;
+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;
 
-	/* Enter the lock */
-	while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
+	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 (synchronized_threads_init() < 0)
+		if (init_common() < 0)
 			ret = -1;
 	}
 
-	/* Exit the lock */
-	InterlockedExchange(&_mutex, 0);
+	if (init_unlock() < 0)
+		return -1;
 
 	return ret;
 }
@@ -175,163 +167,16 @@ int git_libgit2_shutdown(void)
 	int ret;
 
 	/* Enter the lock */
-	while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
+	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) {
+	if ((ret = git_atomic_dec(&git__n_inits)) == 0)
 		shutdown_common();
 
-		FlsFree(_fls_index);
-	}
-
 	/* 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 = FlsGetValue(_fls_index)) != NULL)
-		return ptr;
-
-	ptr = git__calloc(1, sizeof(git_global_st));
-	if (!ptr)
-		return NULL;
-
-	if (git_buf_init(&ptr->error_buf, 0) < 0)
-		return NULL;
-
-	FlsSetValue(_fls_index, ptr);
-	return ptr;
-}
-
-#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)
-{
-	pthread_key_create(&_tls_key, &cb__free_status);
-	init_error = init_common();
-}
-
-int git_libgit2_init(void)
-{
-	int ret, err;
-
-	if ((err = pthread_mutex_lock(&_init_mutex)) != 0)
-		return err;
-
-	ret = git_atomic_inc(&git__n_inits);
-	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 error, ret;
-
-	if ((error = pthread_mutex_lock(&_init_mutex)) != 0)
-		return error;
-
-	if ((ret = git_atomic_dec(&git__n_inits)) != 0)
-		goto out;
-
-	/* 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);
-	_once_init = new_once;
-
-out:
-	if ((error = pthread_mutex_unlock(&_init_mutex)) != 0)
-		return error;
-
-	return ret;
-}
-
-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;
-
-	if (git_buf_init(&ptr->error_buf, 0) < 0)
-		return NULL;
-
-	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));
-	}
+	if (init_unlock() < 0)
+		return -1;
 
 	return ret;
 }
-
-git_global_st *git__global_state(void)
-{
-	return &__state;
-}
-
-#endif /* GIT_THREADS */
diff --git a/src/global.h b/src/global.h
index f4e55eb..0364cab 100644
--- a/src/global.h
+++ b/src/global.h
@@ -9,23 +9,6 @@
 
 #include "common.h"
 
-typedef struct {
-	git_error *last_error;
-	git_error error_t;
-	git_buf error_buf;
-	char oid_fmt[GIT_OID_HEXSZ+1];
-
-	/* On Windows, this is the current child thread that was started by
-	 * `git_thread_create`.  This is used to set the thread's exit code
-	 * when terminated by `git_thread_exit`.  It is unused on POSIX.
-	 */
-	git_thread *current_thread;
-} git_global_st;
-
-git_global_st *git__global_state(void);
-
-#define GIT_GLOBAL (git__global_state())
-
 typedef void (*git_global_shutdown_fn)(void);
 
 extern void git__on_shutdown(git_global_shutdown_fn callback);
diff --git a/src/oid.c b/src/oid.c
index 7831aca..a8ad3d2 100644
--- a/src/oid.c
+++ b/src/oid.c
@@ -9,7 +9,7 @@
 
 #include "git2/oid.h"
 #include "repository.h"
-#include "global.h"
+#include "threadstate.h"
 #include <string.h>
 #include <limits.h>
 
@@ -107,7 +107,7 @@ int git_oid_pathfmt(char *str, const git_oid *oid)
 
 char *git_oid_tostr_s(const git_oid *oid)
 {
-	char *str = GIT_GLOBAL->oid_fmt;
+	char *str = GIT_THREADSTATE->oid_fmt;
 	git_oid_nfmt(str, GIT_OID_HEXSZ + 1, oid);
 	return str;
 }
diff --git a/src/threadstate.c b/src/threadstate.c
new file mode 100644
index 0000000..4aa1c03
--- /dev/null
+++ b/src/threadstate.c
@@ -0,0 +1,161 @@
+/*
+ * 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 "threadstate.h"
+#include "global.h"
+
+static void threadstate_dispose(git_threadstate *threadstate);
+
+/**
+ * Handle the thread-local state
+ *
+ * `git_threadstate_global_init` will be called as part
+ * of `git_libgit2_init` (which itself must be called
+ * before calling any other function in the library).
+ *
+ * This function allocates a TLS index (using pthreads
+ * or fiber-local storage in Win32) to store the per-
+ * thread state.
+ *
+ * Any internal method that requires thread-local state
+ * will then call `git_threadstate_get()` which returns a
+ * pointer to the thread-local state structure; this
+ * structure is lazily allocated on each thread.
+ *
+ * This mechanism will register a shutdown handler
+ * (`git_threadstate_global_shutdown`) which will free the
+ * TLS index.  This shutdown handler will be called by
+ * `git_libgit2_shutdown`.
+ *
+ * If libgit2 is built without threading support, the
+ * `git_threadstate_get()` call returns a pointer to a single,
+ * statically allocated global state. The `git_thread_`
+ * functions are not available in that case.
+ */
+
+#if defined(GIT_THREADS) && defined(GIT_WIN32)
+
+static DWORD fls_index;
+
+static void git_threadstate_global_shutdown(void)
+{
+	FlsFree(fls_index);
+}
+
+static void WINAPI fls_free(void *threadstate)
+{
+	threadstate_dispose(threadstate);
+	git__free(threadstate);
+}
+
+int git_threadstate_global_init(void)
+{
+	if ((fls_index = FlsAlloc(fls_free)) == FLS_OUT_OF_INDEXES)
+		return -1;
+
+	git__on_shutdown(git_threadstate_global_shutdown);
+
+	return 0;
+}
+
+git_threadstate *git_threadstate_get(void)
+{
+	git_threadstate *threadstate;
+
+	if ((threadstate = FlsGetValue(fls_index)) != NULL)
+		return threadstate;
+
+	if ((threadstate = git__calloc(1, sizeof(git_threadstate))) == NULL ||
+	    git_buf_init(&threadstate->error_buf, 0) < 0)
+		return NULL;
+
+	FlsSetValue(fls_index, threadstate);
+	return threadstate;
+}
+
+#elif defined(GIT_THREADS) && defined(_POSIX_THREADS)
+
+static pthread_key_t tls_key;
+
+static void git_threadstate_global_shutdown(void)
+{
+	git_threadstate *threadstate;
+
+	threadstate = pthread_getspecific(tls_key);
+	pthread_setspecific(tls_key, NULL);
+
+	threadstate_dispose(threadstate);
+	git__free(threadstate);
+
+	pthread_key_delete(tls_key);
+}
+
+static void tls_free(void *threadstate)
+{
+	threadstate_dispose(threadstate);
+	git__free(threadstate);
+}
+
+int git_threadstate_global_init(void)
+{
+	if (pthread_key_create(&tls_key, &tls_free) != 0)
+		return -1;
+
+	git__on_shutdown(git_threadstate_global_shutdown);
+
+	return 0;
+}
+
+git_threadstate *git_threadstate_get(void)
+{
+	git_threadstate *threadstate;
+
+	if ((threadstate = pthread_getspecific(tls_key)) != NULL)
+		return threadstate;
+
+	if ((threadstate = git__calloc(1, sizeof(git_threadstate))) == NULL ||
+	    git_buf_init(&threadstate->error_buf, 0) < 0)
+		return NULL;
+
+	pthread_setspecific(tls_key, threadstate);
+	return threadstate;
+}
+
+#elif defined(GIT_THREADS)
+# error unknown threading model
+#else
+
+static git_threadstate threadstate;
+
+static void git_threadstate_global_shutdown(void)
+{
+	threadstate_dispose(&threadstate);
+	memset(&threadstate, 0, sizeof(git_threadstate);
+}
+
+int git_threadstate_global_init(void)
+{
+	git__on_shutdown(git_threadstate_global_shutdown);
+
+	return 0;
+}
+
+git_threadstate *git_threadstate_get(void)
+{
+	return &threadstate;
+}
+
+#endif
+
+static void threadstate_dispose(git_threadstate *threadstate)
+{
+	if (!threadstate)
+		return;
+
+	git__free(threadstate->error_t.message);
+	threadstate->error_t.message = NULL;
+}
diff --git a/src/threadstate.h b/src/threadstate.h
new file mode 100644
index 0000000..9a4ef4d
--- /dev/null
+++ b/src/threadstate.h
@@ -0,0 +1,30 @@
+/*
+ * 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.
+ */
+#ifndef INCLUDE_threadstate_h__
+#define INCLUDE_threadstate_h__
+
+#include "common.h"
+
+typedef struct {
+	git_error *last_error;
+	git_error error_t;
+	git_buf error_buf;
+	char oid_fmt[GIT_OID_HEXSZ+1];
+
+	/* On Windows, this is the current child thread that was started by
+	 * `git_thread_create`.  This is used to set the thread's exit code
+	 * when terminated by `git_thread_exit`.  It is unused on POSIX.
+	 */
+	git_thread *current_thread;
+} git_threadstate;
+
+extern int git_threadstate_global_init(void);
+extern git_threadstate *git_threadstate_get(void);
+
+#define GIT_THREADSTATE (git_threadstate_get())
+
+#endif
diff --git a/src/win32/thread.c b/src/win32/thread.c
index 0936c31..b9f8bc9 100644
--- a/src/win32/thread.c
+++ b/src/win32/thread.c
@@ -7,7 +7,7 @@
 
 #include "thread.h"
 
-#include "../global.h"
+#include "../tlsdata.h"
 
 #define CLEAN_THREAD_EXIT 0x6F012842
 
@@ -28,7 +28,7 @@ static DWORD WINAPI git_win32__threadproc(LPVOID lpParameter)
 	git_thread *thread = lpParameter;
 
 	/* Set the current thread for `git_thread_exit` */
-	GIT_GLOBAL->current_thread = thread;
+	GIT_TLSDATA->current_thread = thread;
 
 	thread->result = thread->proc(thread->param);
 
@@ -99,8 +99,8 @@ int git_thread_join(
 
 void git_thread_exit(void *value)
 {
-	assert(GIT_GLOBAL->current_thread);
-	GIT_GLOBAL->current_thread->result = value;
+	assert(GIT_TLSDATA->current_thread);
+	GIT_TLSDATA->current_thread->result = value;
 	ExitThread(CLEAN_THREAD_EXIT);
 }