Make xmalloc and xrealloc thread-safe

By providing a hook for the routine responsible for trying to free some
memory on malloc failure, we can ensure that the  called routine is
protected by the appropriate locks when threads are in play.

The obvious offender here was pack-objects which was calling xmalloc()
within threads while release_pack_memory() is not thread safe.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/wrapper.c b/wrapper.c
index 9c71b21242..62edb57338 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -3,11 +3,23 @@
  */
 #include "cache.h"
 
+static void try_to_free_builtin(size_t size)
+{
+	release_pack_memory(size, -1);
+}
+
+static void (*try_to_free_routine)(size_t size) = try_to_free_builtin;
+
+void set_try_to_free_routine(void (*routine)(size_t))
+{
+	try_to_free_routine = (routine) ? routine : try_to_free_builtin;
+}
+
 char *xstrdup(const char *str)
 {
 	char *ret = strdup(str);
 	if (!ret) {
-		release_pack_memory(strlen(str) + 1, -1);
+		try_to_free_routine(strlen(str) + 1);
 		ret = strdup(str);
 		if (!ret)
 			die("Out of memory, strdup failed");
@@ -21,7 +33,7 @@ void *xmalloc(size_t size)
 	if (!ret && !size)
 		ret = malloc(1);
 	if (!ret) {
-		release_pack_memory(size, -1);
+		try_to_free_routine(size);
 		ret = malloc(size);
 		if (!ret && !size)
 			ret = malloc(1);
@@ -67,7 +79,7 @@ void *xrealloc(void *ptr, size_t size)
 	if (!ret && !size)
 		ret = realloc(ptr, 1);
 	if (!ret) {
-		release_pack_memory(size, -1);
+		try_to_free_routine(size);
 		ret = realloc(ptr, size);
 		if (!ret && !size)
 			ret = realloc(ptr, 1);
@@ -83,7 +95,7 @@ void *xcalloc(size_t nmemb, size_t size)
 	if (!ret && (!nmemb || !size))
 		ret = calloc(1, 1);
 	if (!ret) {
-		release_pack_memory(nmemb * size, -1);
+		try_to_free_routine(nmemb * size);
 		ret = calloc(nmemb, size);
 		if (!ret && (!nmemb || !size))
 			ret = calloc(1, 1);