Fix T46299: Windows: File Browser Crash while listing big folders in preview mode (fonts, images...).

Windows-only bug, mmap & co are not threadsafe by default on this platform, so we have to add a dedicated
spinlock for them in win32.

Note that we may try to get rid of those mmap later, but not for 2.76!

To be backported to final 2.76...

1 files changed, 24 insertions, 0 deletions

diff --git a/source/blender/imbuf/intern/allocimbuf.c b/source/blender/imbuf/intern/allocimbuf.c
index 5c79eb2c544..19b68b17e70 100644
--- a/source/blender/imbuf/intern/allocimbuf.c
+++ b/source/blender/imbuf/intern/allocimbuf.c
@@ -62,6 +62,30 @@ void imb_refcounter_lock_exit(void)
 	BLI_spin_end(&refcounter_spin);
 }
 
+#ifdef WIN32
+static SpinLock mmap_spin;
+
+void imb_mmap_lock_init(void)
+{
+	BLI_spin_init(&mmap_spin);
+}
+
+void imb_mmap_lock_exit(void)
+{
+	BLI_spin_end(&mmap_spin);
+}
+
+void imb_mmap_lock(void)
+{
+	BLI_spin_lock(&mmap_spin);
+}
+
+void imb_mmap_unlock(void)
+{
+	BLI_spin_unlock(&mmap_spin);
+}
+#endif
+
 void imb_freemipmapImBuf(ImBuf *ibuf)
 {
 	int a;