Thread-safe xmalloc and xrealloc needs a recursive mutex

j6t · gitster · commit 937491944292 · 2010-04-08T23:06:39.000-07:00
The mutex used to protect object access (read_mutex) may need to be acquired recursively. Introduce init_recursive_mutex() helper function in thread-utils.c that constructs a mutex with the PHREAD_MUTEX_RECURSIVE attribute. pthread_mutex_init() emulation on Win32 is already recursive as it is implemented on top of the CRITICAL_SECTION type, which is recursive. http://msdn.microsoft.com/en-us/library/ms682530%28VS.85%29.aspx Add do-nothing compatibility wrappers for pthread_mutexattr* functions. Initial-version-by: Fredrik Kuivinen <frekui@gmail.com> Signed-off-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin-grep.c b/builtin-grep.c
@@ -16,8 +16,8 @@
 #include "quote.h"
 
 #ifndef NO_PTHREADS
-#include "thread-utils.h"
 #include <pthread.h>
+#include "thread-utils.h"
 #endif
 
 static char const * const grep_usage[] = {
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
@@ -18,8 +18,8 @@
 #include "refs.h"
 
 #ifndef NO_PTHREADS
-#include "thread-utils.h"
 #include <pthread.h>
+#include "thread-utils.h"
 #endif
 
 static const char pack_usage[] =
@@ -1586,7 +1586,7 @@ static pthread_cond_t progress_cond;
  */
 static void init_threaded_search(void)
 {
-	pthread_mutex_init(&read_mutex, NULL);
+	init_recursive_mutex(&read_mutex);
 	pthread_mutex_init(&cache_mutex, NULL);
 	pthread_mutex_init(&progress_mutex, NULL);
 	pthread_cond_init(&progress_cond, NULL);
diff --git a/compat/win32/pthread.h b/compat/win32/pthread.h
@@ -18,11 +18,17 @@
  */
 #define pthread_mutex_t CRITICAL_SECTION
 
-#define pthread_mutex_init(a,b) InitializeCriticalSection((a))
+#define pthread_mutex_init(a,b) (InitializeCriticalSection((a)), 0)
 #define pthread_mutex_destroy(a) DeleteCriticalSection((a))
 #define pthread_mutex_lock EnterCriticalSection
 #define pthread_mutex_unlock LeaveCriticalSection
 
+typedef int pthread_mutexattr_t;
+#define pthread_mutexattr_init(a) (*(a) = 0)
+#define pthread_mutexattr_destroy(a) do {} while (0)
+#define pthread_mutexattr_settype(a, t) 0
+#define PTHREAD_MUTEX_RECURSIVE 0
+
 /*
  * Implement simple condition variable for Windows threads, based on ACE
  * implementation.
diff --git a/thread-utils.c b/thread-utils.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include <pthread.h>
 
 #if defined(hpux) || defined(__hpux) || defined(_hpux)
 #  include <sys/pstat.h>
@@ -43,3 +44,18 @@ int online_cpus(void)
 
 	return 1;
 }
+
+int init_recursive_mutex(pthread_mutex_t *m)
+{
+	pthread_mutexattr_t a;
+	int ret;
+
+	ret = pthread_mutexattr_init(&a);
+	if (!ret) {
+		ret = pthread_mutexattr_settype(&a, PTHREAD_MUTEX_RECURSIVE);
+		if (!ret)
+			ret = pthread_mutex_init(m, &a);
+		pthread_mutexattr_destroy(&a);
+	}
+	return ret;
+}
diff --git a/thread-utils.h b/thread-utils.h
@@ -2,5 +2,6 @@
 #define THREAD_COMPAT_H
 
 extern int online_cpus(void);
+extern int init_recursive_mutex(pthread_mutex_t*);
 
 #endif /* THREAD_COMPAT_H */
