Thread-safe xmalloc and xrealloc needs a recursive mutex

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
index 371db0aa9e6572c5b25ea679a510bc8784a25759..52137f4ae4f4fa1f3dd90a43ca88d233cb3b5d41 100644 (file)
--- 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
index 0ecc198422620780740f9589e3771eaee0f8ffd6..26fc7cd5a6f89ce8d8d8c3c56ff039c108ef12f1 100644 (file)
--- 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
index c72f100f40ce2ab9ae7abead730ed00c2a461fbf..a45f8d66df8d1e452d9392945bf12a74c32bbca9 100644 (file)
--- 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
index 4f9c829c2df319e386b6b5d4f5c23818cc21c979..589f838f82b568195232ea81346d0049261b86b1 100644 (file)
--- 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
index cce4b77bd6452e2ec589d8c0dc0e8156352dd67b..1727a03333b80f2a01ca029162a4b511480a86e8 100644 (file)
--- 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 */