Image thread safe improvements

This commit makes BKE_image_acquire_ibuf referencing result, which means once
some area requested for image buffer, it'll be guaranteed this buffer wouldn't
be freed by image signal.

To de-reference buffer BKE_image_release_ibuf should now always be used.

To make referencing working correct we can not rely on result of
image_get_ibuf_threadsafe called outside from thread lock. This is so because
we need to guarantee getting image buffer from list of loaded buffers and it's
referencing happens atomic. Without lock here it is possible that between call
of image_get_ibuf_threadsafe and referencing the buffer IMA_SIGNAL_FREE would
be called. Image signal handling too is blocking now to prevent such a
situation.

Threads are locking by spinlock, which are faster than mutexes. There were some
slowdown reports in the past about render slowdown when using OSX on Xeon CPU.
It shouldn't happen with spin locks, but more tests on different hardware would
be really welcome. So far can not see speed regressions on own computers.

This commit also removes BKE_image_get_ibuf, because it was not so intuitive
when get_ibuf and acquire_ibuf should be used.

Thanks to Ton and Brecht for discussion/review :)

1 files changed, 17 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_threads.h b/source/blender/blenlib/BLI_threads.h
index 9cd801f819d..ec8e567c0ef 100644
--- a/source/blender/blenlib/BLI_threads.h
+++ b/source/blender/blenlib/BLI_threads.h
@@ -37,6 +37,10 @@ extern "C" {
 
 #include <pthread.h>
 
+#ifdef __APPLE__
+#include <libkern/OSAtomic.h>
+#endif
+
 /* for tables, button in UI, etc */
 #define BLENDER_MAX_THREADS     64
 
@@ -92,6 +96,19 @@ void BLI_mutex_lock(ThreadMutex *mutex);
 void BLI_mutex_unlock(ThreadMutex *mutex);
 void BLI_mutex_end(ThreadMutex *mutex);
 
+/* Spin Lock */
+
+#ifdef __APPLE__
+typedef OSSpinLock SpinLock;
+#else
+typedef pthread_spinlock_t SpinLock;
+#endif
+
+void BLI_spin_init(SpinLock *spin);
+void BLI_spin_lock(SpinLock *spin);
+void BLI_spin_unlock(SpinLock *spin);
+void BLI_spin_end(SpinLock *spin);
+
 /* Read/Write Mutex Lock */
 
 #define THREAD_LOCK_READ    1