hevc: fix race condition in max_ra/seq_decode.

These variables are shared between frame threads, but they are updated
post-setup_finished() if a EOB/EOS slice type occurs. Moving the EOB/EOS
slices to the next frame thread instance (by parsing them leading into
the next picture instead of trailing behind the last picture) effectively
prevents this race condition.

This fixes tsan failures on hevc-conformance-NoOutPrior_A_Qualcomm_1.

libavcodec/hevc_parser.c

@@ -267,7 +267,7 @@ static int hevc_find_frame_end(AVCodecParserContext *s, const uint8_t *buf,
 
         nut = (pc->state64 >> 2 * 8 + 1) & 0x3F;
         // Beginning of access unit
-        if ((nut >= HEVC_NAL_VPS && nut <= HEVC_NAL_AUD) || nut == HEVC_NAL_SEI_PREFIX ||
+        if ((nut >= HEVC_NAL_VPS && nut <= HEVC_NAL_EOB_NUT) || nut == HEVC_NAL_SEI_PREFIX ||
             (nut >= 41 && nut <= 44) || (nut >= 48 && nut <= 55)) {
             if (pc->frame_start_found) {
                 pc->frame_start_found = 0;

libavcodec/hevcdec.c

@@ -2890,6 +2890,7 @@ fail:
 static int decode_nal_units(HEVCContext *s, const uint8_t *buf, int length)
 {
     int i, ret = 0;
+    int eos_at_start = 1;
 
     s->ref = NULL;
     s->last_eos = s->eos;
@@ -2907,8 +2908,15 @@ static int decode_nal_units(HEVCContext *s, const uint8_t *buf, int length)
 
     for (i = 0; i < s->pkt.nb_nals; i++) {
         if (s->pkt.nals[i].type == HEVC_NAL_EOB_NUT ||
-            s->pkt.nals[i].type == HEVC_NAL_EOS_NUT)
-            s->eos = 1;
+            s->pkt.nals[i].type == HEVC_NAL_EOS_NUT) {
+            if (eos_at_start) {
+                s->last_eos = 1;
+            } else {
+                s->eos = 1;
+            }
+        } else {
+            eos_at_start = 0;
+        }
     }
 
     /* decode the NAL units */