[FFmpeg-devel] [RFC PATCH] avfilter/video: Protect frame_pool from multi-threads access

[Zhao Zhili]

From: Zhao Zhili <zhilizhao at tencent.com>

Fix crash with
./ffplay -f lavfi -i movie=foo.mp4,drawtext=text=bar
---
 libavfilter/avfilter.c          |  2 ++
 libavfilter/avfilter_internal.h |  2 ++
 libavfilter/video.c             | 14 ++++++++------
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 049e4f62ca..44da809c15 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -176,6 +176,7 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
     li = av_mallocz(sizeof(*li));
     if (!li)
         return AVERROR(ENOMEM);
+    ff_mutex_init(&li->frame_pool_mutex, NULL);
     link = &li->l;
 
     src->outputs[srcpad] = dst->inputs[dstpad] = link;
@@ -203,6 +204,7 @@ static void link_free(AVFilterLink **link)
 
     ff_framequeue_free(&li->fifo);
     ff_frame_pool_uninit(&li->frame_pool);
+    ff_mutex_destroy(&li->frame_pool_mutex);
     av_channel_layout_uninit(&(*link)->ch_layout);
 
     av_freep(link);
diff --git a/libavfilter/avfilter_internal.h b/libavfilter/avfilter_internal.h
index 2c31c3e7de..eae3a699c3 100644
--- a/libavfilter/avfilter_internal.h
+++ b/libavfilter/avfilter_internal.h
@@ -27,6 +27,7 @@
 
 #include <stdint.h>
 
+#include "libavutil/thread.h"
 #include "avfilter.h"
 #include "framequeue.h"
 
@@ -34,6 +35,7 @@ typedef struct FilterLinkInternal {
     AVFilterLink l;
 
     struct FFFramePool *frame_pool;
+    AVMutex frame_pool_mutex;
 
     /**
      * Queue of frames waiting to be filtered.
diff --git a/libavfilter/video.c b/libavfilter/video.c
index 89d0797ab5..30eba76cbd 100644
--- a/libavfilter/video.c
+++ b/libavfilter/video.c
@@ -70,17 +70,17 @@ AVFrame *ff_default_get_video_buffer2(AVFilterLink *link, int w, int h, int alig
         return frame;
     }
 
+    ff_mutex_lock(&li->frame_pool_mutex);
     if (!li->frame_pool) {
         li->frame_pool = ff_frame_pool_video_init(av_buffer_allocz, w, h,
                                                   link->format, align);
         if (!li->frame_pool)
-            return NULL;
+            goto out;
     } else {
         if (ff_frame_pool_get_video_config(li->frame_pool,
                                            &pool_width, &pool_height,
-                                           &pool_format, &pool_align) < 0) {
-            return NULL;
-        }
+                                           &pool_format, &pool_align) < 0)
+            goto out;
 
         if (pool_width != w || pool_height != h ||
             pool_format != link->format || pool_align != align) {
@@ -89,18 +89,20 @@ AVFrame *ff_default_get_video_buffer2(AVFilterLink *link, int w, int h, int alig
             li->frame_pool = ff_frame_pool_video_init(av_buffer_allocz, w, h,
                                                       link->format, align);
             if (!li->frame_pool)
-                return NULL;
+                goto out;
         }
     }
 
     frame = ff_frame_pool_get(li->frame_pool);
     if (!frame)
-        return NULL;
+        goto out;
 
     frame->sample_aspect_ratio = link->sample_aspect_ratio;
     frame->colorspace  = link->colorspace;
     frame->color_range = link->color_range;
 
+out:
+    ff_mutex_unlock(&li->frame_pool_mutex);
     return frame;
 }
 
-- 
2.42.0