sub: uglify sub decoder with locking

The plan is to make the whole OSD thread-safe, and we start with this.

We just put locks on all entry points (fortunately, dec_sub.c and all
sd_*.c decoders are very closed off, and only the entry points in
dec_sub.h let you access it). I think this is pretty ugly, but at least
it's very simple.

There's a special case with sub_get_bitmaps(): this function returns
pointers to decoder data (specifically, libass images). There's no way
to synchronize this internally, so expose sub_lock/sub_unlock functions.

To make things simpler, and especially because the lock is sort-of
exposed to the outside world, make the locks recursive. Although the
only case where this is actually needed (although trivial) is
sub_set_extradata().

One corner case are ASS subtitles: for some reason, we keep a single
ASS_Renderer instance for subtitles around (probably to avoid rescanning
fonts with ordered chapters), and this ASS_Renderer instance is not
synchronized. Also, demux_libass.c loads ASS_Track objects, which are
directly passed to sd_ass.c. These things are not synchronized (and
would be hard to synchronize), and basically we're out of luck. But I
think for now, accesses happen reasonably serialized, so there is no
actual problem yet, even if we start to access OSD from other threads.

1 files changed, 6 insertions, 0 deletions

diff --git a/sub/osd.c b/sub/osd.c
index 16c1288f5d..56d845b97f 100644
--- a/sub/osd.c
+++ b/sub/osd.c
@@ -246,6 +246,9 @@ void osd_draw(struct osd_state *osd, struct mp_osd_res res,
         if ((draw_flags & OSD_DRAW_SUB_ONLY) && !obj->is_sub)
             continue;
 
+        if (obj->dec_sub)
+            sub_lock(obj->dec_sub);
+
         struct sub_bitmaps imgs;
         render_object(osd, obj, res, video_pts, formats, &imgs);
         if (imgs.num_parts > 0) {
@@ -256,6 +259,9 @@ void osd_draw(struct osd_state *osd, struct mp_osd_res res,
                        obj->type, imgs.format);
             }
         }
+
+        if (obj->dec_sub)
+            sub_unlock(obj->dec_sub);
     }
 }