[FFmpeg-devel] [PATCH 216/217] avcodec/h263data, ituh263*: Make initializing RL tables thread-safe

[Andreas Rheinhardt]

Up until now, ff_h263_rl_inter and ff_rl_intra_aic were initialized by
both ituh263dec and ituh263enc; the result was that although
ff_h263_encode_init() guards the initialization of its static data with
an AVOnce, initializing the aforementioned RLTables was still not
thread-safe because ff_h263_decode_init_vlc() might try to initialize it
at the same time.

This is fixed by only initializing these RLTables from a single place
that is guarded by a dedicated AVOnce.

This also makes the Snow encoder actually init-threadsafe; it was
already wrongly marked as init-threadsafe since commit
d49210788b0836d56dd872d517fe73f83b080101.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/h263data.c   | 16 +++++++++++++++-
 libavcodec/h263data.h   |  2 +-
 libavcodec/ituh263dec.c |  3 +--
 libavcodec/ituh263enc.c |  3 +--
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/libavcodec/h263data.c b/libavcodec/h263data.c
index f649d58f4e..8fd97100f4 100644
--- a/libavcodec/h263data.c
+++ b/libavcodec/h263data.c
@@ -25,10 +25,12 @@
 
 #include <stdint.h>
 
+#include "libavutil/thread.h"
+
 #include "h263data.h"
 #include "mpegvideo.h"
 
-uint8_t ff_h263_static_rl_table_store[2][2][2 * MAX_RUN + MAX_LEVEL + 3];
+static uint8_t h263_static_rl_table_store[2][2][2 * MAX_RUN + MAX_LEVEL + 3];
 
 /* intra MCBPC, mb_type = (intra), then (intraq) */
 const uint8_t ff_h263_intra_MCBPC_code[9] = { 1, 1, 2, 3, 1, 1, 2, 3, 1 };
@@ -290,3 +292,15 @@ const AVRational ff_h263_pixel_aspect[16] = {
     {  0,  1 },
     {  0,  1 },
 };
+
+static av_cold void h263_init_rl(void)
+{
+    ff_rl_init(&ff_h263_rl_inter, h263_static_rl_table_store[0]);
+    ff_rl_init(&ff_rl_intra_aic,  h263_static_rl_table_store[1]);
+}
+
+av_cold void ff_h263_init_rl(void)
+{
+    static AVOnce init_static_once = AV_ONCE_INIT;
+    ff_thread_once(&init_static_once, h263_init_rl);
+}
diff --git a/libavcodec/h263data.h b/libavcodec/h263data.h
index 3da0e3771f..4a619f586e 100644
--- a/libavcodec/h263data.h
+++ b/libavcodec/h263data.h
@@ -61,7 +61,7 @@ extern const int8_t ff_inter_run[102];
 
 extern RLTable ff_h263_rl_inter;
 extern RLTable ff_rl_intra_aic;
-extern uint8_t ff_h263_static_rl_table_store[2][2][2 * MAX_RUN + MAX_LEVEL + 3];
+void ff_h263_init_rl(void);
 
 extern const uint16_t ff_h263_format[8][2];
 
diff --git a/libavcodec/ituh263dec.c b/libavcodec/ituh263dec.c
index c1005b0994..7791093cfc 100644
--- a/libavcodec/ituh263dec.c
+++ b/libavcodec/ituh263dec.c
@@ -122,8 +122,7 @@ av_cold void ff_h263_decode_init_vlc(void)
         INIT_VLC_STATIC(&mv_vlc, MV_VLC_BITS, 33,
                  &ff_mvtab[0][1], 2, 1,
                  &ff_mvtab[0][0], 2, 1, 538);
-        ff_rl_init(&ff_h263_rl_inter, ff_h263_static_rl_table_store[0]);
-        ff_rl_init(&ff_rl_intra_aic, ff_h263_static_rl_table_store[1]);
+        ff_h263_init_rl();
         INIT_VLC_RL(ff_h263_rl_inter, 554);
         INIT_VLC_RL(ff_rl_intra_aic, 554);
         INIT_VLC_STATIC(&h263_mbtype_b_vlc, H263_MBTYPE_B_VLC_BITS, 15,
diff --git a/libavcodec/ituh263enc.c b/libavcodec/ituh263enc.c
index 88d003ed47..10d34671e1 100644
--- a/libavcodec/ituh263enc.c
+++ b/libavcodec/ituh263enc.c
@@ -757,8 +757,7 @@ static av_cold void init_uni_h263_rl_tab(const RLTable *rl, uint8_t *len_tab)
 
 static av_cold void h263_encode_init_static(void)
 {
-    ff_rl_init(&ff_h263_rl_inter, ff_h263_static_rl_table_store[0]);
-    ff_rl_init(&ff_rl_intra_aic, ff_h263_static_rl_table_store[1]);
+    ff_h263_init_rl();
 
     init_uni_h263_rl_tab(&ff_rl_intra_aic,  uni_h263_intra_aic_rl_len);
     init_uni_h263_rl_tab(&ff_h263_rl_inter, uni_h263_inter_rl_len);
-- 
2.25.1