[PATCH] MSVC: Windows-native implementation for subset of Pthreads API

From

Andrzej K. Haczewski <ahaczewski@gmail.com>

Date

Nov 6, 2009, 08:10 UTC

Message-ID

<1257495059-12394-1-git-send-email-ahaczewski@gmail.com>

In-Reply-To

<1257283802-29726-1-git-send-email-ahaczewski@gmail.com>

Signed-off-by: Andrzej K. Haczewski <ahaczewski@gmail.com>
---
One more round of that patch with Nicolas' comments considered, and
disclamer about the implementation added.

Johannes, can you replace previous commit with that patch?

 Makefile               |    7 ++-
 builtin-pack-objects.c |   31 +++++++++++--
 compat/mingw.c         |    2 +-
 compat/mingw.h         |    5 ++
 compat/win32/pthread.c |  120 ++++++++++++++++++++++++++++++++++++++++++++++++
 compat/win32/pthread.h |   68 +++++++++++++++++++++++++++
 6 files changed, 225 insertions(+), 8 deletions(-)
 create mode 100644 compat/win32/pthread.c
 create mode 100644 compat/win32/pthread.h

diff --git a/Makefile b/Makefile
index bc039ac..30089a8 100644
--- a/Makefile
+++ b/Makefile
@@ -453,6 +453,7 @@ LIB_H += commit.h
 LIB_H += compat/bswap.h
 LIB_H += compat/cygwin.h
 LIB_H += compat/mingw.h
+LIB_H += compat/win32/pthread.h
 LIB_H += csum-file.h
 LIB_H += decorate.h
 LIB_H += delta.h
@@ -971,15 +972,15 @@ ifdef MSVC
 	OBJECT_CREATION_USES_RENAMES = UnfortunatelyNeedsTo
 	NO_REGEX = YesPlease
 	NO_CURL = YesPlease
-	NO_PTHREADS = YesPlease
+	THREADED_DELTA_SEARCH = YesPlease
 	BLK_SHA1 = YesPlease
 
 	CC = compat/vcbuild/scripts/clink.pl
 	AR = compat/vcbuild/scripts/lib.pl
 	CFLAGS =
 	BASIC_CFLAGS = -nologo -I. -I../zlib -Icompat/vcbuild -Icompat/vcbuild/include -DWIN32 -D_CONSOLE -DHAVE_STRING_H -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE
-	COMPAT_OBJS = compat/msvc.o compat/fnmatch/fnmatch.o compat/winansi.o
-	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -DHAVE_ALLOCA_H -Icompat -Icompat/fnmatch -Icompat/regex -Icompat/fnmatch -DSTRIP_EXTENSION=\".exe\"
+	COMPAT_OBJS = compat/msvc.o compat/fnmatch/fnmatch.o compat/winansi.o compat/win32/pthread.o
+	COMPAT_CFLAGS = -D__USE_MINGW_ACCESS -DNOGDI -DHAVE_STRING_H -DHAVE_ALLOCA_H -Icompat -Icompat/fnmatch -Icompat/regex -Icompat/fnmatch -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
 	BASIC_LDFLAGS = -IGNORE:4217 -IGNORE:4049 -NOLOGO -SUBSYSTEM:CONSOLE -NODEFAULTLIB:MSVCRT.lib
 	EXTLIBS = advapi32.lib shell32.lib wininet.lib ws2_32.lib
 	lib =
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 02f9246..00594fd 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -1255,15 +1255,15 @@ static int delta_cacheable(unsigned long src_size, unsigned long trg_size,
 
 #ifdef THREADED_DELTA_SEARCH
 
-static pthread_mutex_t read_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t read_mutex;
 #define read_lock()		pthread_mutex_lock(&read_mutex)
 #define read_unlock()		pthread_mutex_unlock(&read_mutex)
 
-static pthread_mutex_t cache_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t cache_mutex;
 #define cache_lock()		pthread_mutex_lock(&cache_mutex)
 #define cache_unlock()		pthread_mutex_unlock(&cache_mutex)
 
-static pthread_mutex_t progress_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t progress_mutex;
 #define progress_lock()		pthread_mutex_lock(&progress_mutex)
 #define progress_unlock()	pthread_mutex_unlock(&progress_mutex)
 
@@ -1590,7 +1590,26 @@ struct thread_params {
 	unsigned *processed;
 };
 
-static pthread_cond_t progress_cond = PTHREAD_COND_INITIALIZER;
+static pthread_cond_t progress_cond;
+
+/*
+ * Mutex and conditional variable can't be statically-initialized on Windows.
+ */
+static void init_threaded_search()
+{
+	pthread_mutex_init(&read_mutex, NULL);
+	pthread_mutex_init(&cache_mutex, NULL);
+	pthread_mutex_init(&progress_mutex, NULL);
+	pthread_cond_init(&progress_cond, NULL);
+}
+
+static void cleanup_threaded_search()
+{
+	pthread_cond_destroy(&progress_cond);
+	pthread_mutex_destroy(&read_mutex);
+	pthread_mutex_destroy(&cache_mutex);
+	pthread_mutex_destroy(&progress_mutex);
+}
 
 static void *threaded_find_deltas(void *arg)
 {
@@ -1629,8 +1648,11 @@ static void ll_find_deltas(struct object_entry **list, unsigned list_size,
 	struct thread_params *p;
 	int i, ret, active_threads = 0;
 
+	init_threaded_search();
+
 	if (delta_search_threads <= 1) {
 		find_deltas(list, &list_size, window, depth, processed);
+		cleanup_threaded_search();
 		return;
 	}
 	if (progress > pack_to_stdout)
@@ -1745,6 +1767,7 @@ static void ll_find_deltas(struct object_entry **list, unsigned list_size,
 			active_threads--;
 		}
 	}
+	cleanup_threaded_search();
 	free(p);
 }
 
diff --git a/compat/mingw.c b/compat/mingw.c
index 6b5b5b2..f2e9f02 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -5,7 +5,7 @@
 
 #include <shellapi.h>
 
-static int err_win_to_posix(DWORD winerr)
+int err_win_to_posix(DWORD winerr)
 {
 	int error = ENOSYS;
 	switch(winerr) {
diff --git a/compat/mingw.h b/compat/mingw.h
index 6907345..7e25fb5 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -294,3 +294,8 @@ struct mingw_dirent
 #define readdir(x) mingw_readdir(x)
 struct dirent *mingw_readdir(DIR *dir);
 #endif // !NO_MINGW_REPLACE_READDIR
+
+/*
+ * Used by Pthread API implementation for Windows
+ */
+extern int err_win_to_posix(DWORD winerr);
diff --git a/compat/win32/pthread.c b/compat/win32/pthread.c
new file mode 100644
index 0000000..652d7b4
--- /dev/null
+++ b/compat/win32/pthread.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2009 Andrzej K. Haczewski <ahaczewski@gmail.com>
+ *
+ * DISCLAMER: The implementation is Git-specific, it is subset of original
+ * Pthreads API, without lots of other features that Git doesn't use.
+ * Git also makes sure that the passed arguments are valid, so there's
+ * no need for double-checking.
+ */
+
+#include "../../git-compat-util.h"
+#include "pthread.h"
+
+#include <errno.h>
+#include <limits.h>
+
+static unsigned __stdcall win32_start_routine(void *arg)
+{
+	pthread_t *thread = arg;
+	thread->arg = thread->start_routine(thread->arg);
+	return 0;
+}
+
+int pthread_create(pthread_t *thread, const void *unused,
+		   void *(*start_routine)(void*), void *arg)
+{
+	thread->arg = arg;
+	thread->start_routine = start_routine;
+	thread->handle = (HANDLE)
+		_beginthreadex(NULL, 0, win32_start_routine, thread, 0, NULL);
+
+	if (!thread->handle)
+		return errno;
+	else
+		return 0;
+}
+
+int win32_pthread_join(pthread_t *thread, void **value_ptr)
+{
+	DWORD result = WaitForSingleObject(thread->handle, INFINITE);
+	switch (result) {
+		case WAIT_OBJECT_0:
+			if (value_ptr)
+				*value_ptr = thread->arg;
+			return 0;
+		case WAIT_ABANDONED:
+			return EINVAL;
+		default:
+			return err_win_to_posix(GetLastError());
+	}
+}
+
+int pthread_cond_init(pthread_cond_t *cond, const void *unused)
+{
+	cond->waiters = 0;
+
+	InitializeCriticalSection(&cond->waiters_lock);
+
+	cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
+	if (!cond->sema)
+		die("CreateSemaphore() failed");
+	return 0;
+}
+
+int pthread_cond_destroy(pthread_cond_t *cond)
+{
+	CloseHandle(cond->sema);
+	cond->sema = NULL;
+
+	DeleteCriticalSection(&cond->waiters_lock);
+
+	return 0;
+}
+
+int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex)
+{
+	/* serialize access to waiters count */
+	EnterCriticalSection(&cond->waiters_lock);
+	++cond->waiters;
+	LeaveCriticalSection(&cond->waiters_lock);
+
+	/*
+	 * Unlock external mutex and wait for signal.
+	 * NOTE: we've held mutex locked long enough to increment
+	 * waiters count above, so there's no problem with
+	 * leaving mutex unlocked before we wait on semaphore.
+	 */
+	LeaveCriticalSection(mutex);
+
+	/* let's wait - ignore return value */
+	WaitForSingleObject(cond->sema, INFINITE);
+
+	/* we're done waiting, so make sure we decrease waiters count */
+	EnterCriticalSection(&cond->waiters_lock);
+	--cond->waiters;
+	LeaveCriticalSection(&cond->waiters_lock);
+
+	/* lock external mutex again */
+	EnterCriticalSection(mutex);
+
+	return 0;
+}
+
+int pthread_cond_signal(pthread_cond_t *cond)
+{
+	int have_waiters;
+
+	/* serialize access to waiters count */
+	EnterCriticalSection(&cond->waiters_lock);
+	have_waiters = cond->waiters > 0;
+	LeaveCriticalSection(&cond->waiters_lock);
+
+	/*
+	 * Signal only when there are waiters
+	 */
+	if (have_waiters)
+		return ReleaseSemaphore(cond->sema, 1, NULL) ?
+			0 : err_win_to_posix(GetLastError());
+	else
+		return 0;
+}
diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
new file mode 100644
index 0000000..63293ad
--- /dev/null
+++ b/compat/win32/pthread.h
@@ -0,0 +1,68 @@
+/*
+ * Header used to adapt pthread-based POSIX code to Windows API threads.
+ *
+ * Copyright (C) 2009 Andrzej K. Haczewski <ahaczewski@gmail.com>
+ */
+
+#ifndef PTHREAD_H
+#define PTHREAD_H
+
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+
+#include <windows.h>
+
+/*
+ * Defines that adapt Windows API threads to pthreads API
+ */
+#define pthread_mutex_t CRITICAL_SECTION
+
+#define pthread_mutex_init(a,b) InitializeCriticalSection((a))
+#define pthread_mutex_destroy(a) DeleteCriticalSection((a))
+#define pthread_mutex_lock EnterCriticalSection
+#define pthread_mutex_unlock LeaveCriticalSection
+
+/*
+ * Implement simple condition variable for Windows threads, based on ACE
+ * implementation.
+ *
+ * See original implementation: http://bit.ly/1vkDjo
+ * ACE homepage: http://www.cse.wustl.edu/~schmidt/ACE.html
+ * See also: http://www.cse.wustl.edu/~schmidt/win32-cv-1.html
+ */
+typedef struct {
+	LONG waiters;
+	CRITICAL_SECTION waiters_lock;
+	HANDLE sema;
+} pthread_cond_t;
+
+extern int pthread_cond_init(pthread_cond_t *cond, const void *unused);
+
+extern int pthread_cond_destroy(pthread_cond_t *cond);
+
+extern int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex);
+
+extern int pthread_cond_signal(pthread_cond_t *cond);
+
+/*
+ * Simple thread creation implementation using pthread API
+ */
+typedef struct {
+	HANDLE handle;
+	void *(*start_routine)(void*);
+	void *arg;
+} pthread_t;
+
+extern int pthread_create(pthread_t *thread, const void *unused,
+			  void *(*start_routine)(void*), void *arg);
+
+/*
+ * To avoid the need of copying a struct, we use small macro wrapper to pass
+ * pointer to win32_pthread_join instead.
+ */
+#define pthread_join(a, b) win32_pthread_join(&(a), (b))
+
+extern int win32_pthread_join(pthread_t *thread, void **value_ptr);
+
+#endif /* PTHREAD_H */

-- 
1.6.5.2