Simplifies decoder multithread synching

Increment the last_row_mb_col counter by nsync after last MB of row is
ready. This way we dont need to check for last MB of row when
synching.

Set last MB of row ready just after row extension is done, This avoids
o potential race condition whit the processing of last MB of next row.

Change-Id: I19c44fd6041116ee5483be2143b4f4bfcd149eac

2 files changed, 39 insertions, 51 deletions

diff --git a/vp8/decoder/onyxd_int.h b/vp8/decoder/onyxd_int.h
index 97cf0dcea..f2b9c60b5 100644
--- a/vp8/decoder/onyxd_int.h
+++ b/vp8/decoder/onyxd_int.h
@@ -31,7 +31,6 @@ typedef struct
 typedef struct
 {
     MACROBLOCKD  mbd;
-    int mb_row;
 } MB_ROW_DEC;
 
 typedef struct
diff --git a/vp8/decoder/threading.c b/vp8/decoder/threading.c
index befdbdeaa..25dc6fe08 100644
--- a/vp8/decoder/threading.c
+++ b/vp8/decoder/threading.c
@@ -71,16 +71,18 @@ static void setup_decoding_thread_data(VP8D_COMP *pbi, MACROBLOCKD *xd, MB_ROW_D
         vpx_memcpy(mbd->dequant_uv, xd->dequant_uv, sizeof(xd->dequant_uv));
 
         mbd->fullpixel_mask = 0xffffffff;
-        if(pc->full_pixel)
+
+        if (pc->full_pixel)
             mbd->fullpixel_mask = 0xfffffff8;
 
     }
 
-    for (i=0; i< pc->mb_rows; i++)
-        pbi->mt_current_mb_col[i]=-1;
+    for (i = 0; i < pc->mb_rows; i++)
+        pbi->mt_current_mb_col[i] = -1;
 }
 
-static void decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd, unsigned int mb_idx)
+static void mt_decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd,
+                                 unsigned int mb_idx)
 {
     MB_PREDICTION_MODE mode;
     int i;
@@ -295,34 +297,16 @@ static void decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd, unsigned int mb_i
     }
 }
 
-typedef void (*init_current_bc_fn_t)(VP8D_COMP *pbi, MACROBLOCKD *xd,
-    int start_mb_row, int mb_row, int num_part);
-
-static void init_current_bc(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
-                     int mb_row, int num_part)
-{
-    (void) start_mb_row;
-
-    xd->current_bc = &pbi->mbc[mb_row%num_part];
-}
-
-static void init_current_bc_threads(VP8D_COMP *pbi, MACROBLOCKD *xd,
-                     int start_mb_row, int mb_row, int num_part)
+static void mt_decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row)
 {
-    (void) xd;
-    pbi->mb_row_di[start_mb_row - 1].mb_row = mb_row;
-    pbi->mb_row_di[start_mb_row - 1].mbd.current_bc =  &pbi->mbc[mb_row%num_part];
-}
-
-
-static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
-                           init_current_bc_fn_t init_current_bc_fn)
-{
-    volatile int *last_row_current_mb_col = NULL;
+    volatile const int *last_row_current_mb_col;
+    volatile int *current_mb_col;
     int mb_row;
     VP8_COMMON *pc = &pbi->common;
-    int nsync = pbi->sync_range;
+    const int nsync = pbi->sync_range;
+    const int first_row_no_sync_above = pc->mb_cols + nsync;
     int num_part = 1 << pbi->common.multi_token_partition;
+    int last_mb_row = start_mb_row;
 
     int dst_fb_idx = pc->new_fb_idx;
     unsigned char *ref_buffer[MAX_REF_FRAMES][3];
@@ -365,10 +349,17 @@ static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
        int filter_level;
        loop_filter_info_n *lfi_n = &pc->lf_info;
 
-       init_current_bc_fn(pbi, xd, start_mb_row, mb_row, num_part);
+       /* save last row processed by this thread */
+       last_mb_row = mb_row;
+       /* select bool coder for current partition */
+       xd->current_bc =  &pbi->mbc[mb_row%num_part];
 
        if (mb_row > 0)
            last_row_current_mb_col = &pbi->mt_current_mb_col[mb_row -1];
+       else
+           last_row_current_mb_col = &first_row_no_sync_above;
+
+       current_mb_col = &pbi->mt_current_mb_col[mb_row];
 
        recon_yoffset = mb_row * recon_y_stride * 16;
        recon_uvoffset = mb_row * recon_uv_stride * 8;
@@ -417,9 +408,11 @@ static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
 
        for (mb_col = 0; mb_col < pc->mb_cols; mb_col++)
        {
-           if ( mb_row > 0 && (mb_col & (nsync-1)) == 0)
+           *current_mb_col = mb_col - 1;
+
+           if ((mb_col & (nsync - 1)) == 0)
            {
-               while (mb_col > (*last_row_current_mb_col - nsync) && *last_row_current_mb_col != pc->mb_cols - 1)
+               while (mb_col > (*last_row_current_mb_col - nsync))
                {
                    x86_pause_hint();
                    thread_sleep(0);
@@ -475,7 +468,7 @@ static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
            /* propagate errors from reference frames */
            xd->corrupted |= ref_fb_corrupted[xd->mode_info_context->mbmi.ref_frame];
 
-           decode_macroblock(pbi, xd, 0);
+           mt_decode_macroblock(pbi, xd, 0);
 
            xd->left_available = 1;
 
@@ -589,9 +582,6 @@ static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
            ++xd->mode_info_context;  /* next mb */
 
            xd->above_context++;
-
-           /*pbi->mb_row_di[ithread].current_mb_col = mb_col;*/
-           pbi->mt_current_mb_col[mb_row] = mb_col;
        }
 
        /* adjust to the next row of mbs */
@@ -609,8 +599,13 @@ static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
                    pbi->mt_vabove_row[mb_row +1][lastuv + i] = pbi->mt_vabove_row[mb_row +1][lastuv -1];
                }
            }
-       } else
-           vp8_extend_mb_row(&pc->yv12_fb[dst_fb_idx], xd->dst.y_buffer + 16, xd->dst.u_buffer + 8, xd->dst.v_buffer + 8);
+       }
+       else
+           vp8_extend_mb_row(&pc->yv12_fb[dst_fb_idx], xd->dst.y_buffer + 16,
+                             xd->dst.u_buffer + 8, xd->dst.v_buffer + 8);
+
+       /* last MB of row is ready just after extension is done */
+       *current_mb_col = mb_col + nsync;
 
        ++xd->mode_info_context;      /* skip prediction column */
        xd->up_available = 1;
@@ -618,6 +613,11 @@ static void decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd, int start_mb_row,
        /* since we have multithread */
        xd->mode_info_context += xd->mode_info_stride * pbi->decoding_thread_count;
     }
+
+    /* signal end of frame decoding if this thread processed the last mb_row */
+    if (last_mb_row == (pc->mb_rows - 1))
+        sem_post(&pbi->h_event_end_decoding);
+
 }
 
 
@@ -633,7 +633,6 @@ static THREAD_FUNCTION thread_decoding_proc(void *p_data)
         if (pbi->b_multithreaded_rd == 0)
             break;
 
-        /*if(WaitForSingleObject(pbi->h_event_start_decoding[ithread], INFINITE) == WAIT_OBJECT_0)*/
         if (sem_wait(&pbi->h_event_start_decoding[ithread]) == 0)
         {
             if (pbi->b_multithreaded_rd == 0)
@@ -641,21 +640,11 @@ static THREAD_FUNCTION thread_decoding_proc(void *p_data)
             else
             {
                 MACROBLOCKD *xd = &mbrd->mbd;
-
                 xd->left_context = &mb_row_left_context;
 
-                decode_mb_rows(pbi, xd, ithread+1, init_current_bc_threads);
+                mt_decode_mb_rows(pbi, xd, ithread+1);
             }
         }
-
-        /*  add this to each frame */
-        if ((mbrd->mb_row == pbi->common.mb_rows-1) ||
-            ((mbrd->mb_row == pbi->common.mb_rows-2) &&
-                (pbi->common.mb_rows % (pbi->decoding_thread_count+1))==1))
-        {
-            /*SetEvent(pbi->h_event_end_decoding);*/
-            sem_post(&pbi->h_event_end_decoding);
-        }
     }
 
     return 0 ;
@@ -916,7 +905,7 @@ void vp8mt_decode_mb_rows( VP8D_COMP *pbi, MACROBLOCKD *xd)
     for (i = 0; i < pbi->decoding_thread_count; i++)
         sem_post(&pbi->h_event_start_decoding[i]);
 
-    decode_mb_rows(pbi, xd, 0, init_current_bc);
+    mt_decode_mb_rows(pbi, xd, 0);
 
     sem_wait(&pbi->h_event_end_decoding);   /* add back for each frame */
 }