Reapply 'Amend and improve VP8 multithreading implementation'

Reapply this patch:
ff0107f Amend and improve VP8 multithreading implementation

Amended the patch to add a unit test, and fix an asan error.

BUG=webm:851

Change-Id: I6572c03256169c64e80248bf5a5e99f59a2fc93c

2 files changed, 44 insertions, 19 deletions

diff --git a/vp8/decoder/onyxd_int.h b/vp8/decoder/onyxd_int.h
index e50fafd4f..88b1ff16b 100644
--- a/vp8/decoder/onyxd_int.h
+++ b/vp8/decoder/onyxd_int.h
@@ -67,7 +67,8 @@ typedef struct VP8D_COMP {
 
 #if CONFIG_MULTITHREAD
   /* variable for threading */
-  volatile int b_multithreaded_rd;
+
+  int b_multithreaded_rd;
   int max_threads;
   int current_mb_col_main;
   unsigned int decoding_thread_count;
@@ -76,6 +77,8 @@ typedef struct VP8D_COMP {
   int mt_baseline_filter_level[MAX_MB_SEGMENTS];
   int sync_range;
   int *mt_current_mb_col; /* Each row remembers its already decoded column. */
+  pthread_mutex_t *pmutex;
+  pthread_mutex_t mt_mutex; /* mutex for b_multithreaded_rd */
 
   unsigned char **mt_yabove_row; /* mb_rows x width */
   unsigned char **mt_uabove_row;
diff --git a/vp8/decoder/threading.c b/vp8/decoder/threading.c
index 44ca16bfd..5b6200f67 100644
--- a/vp8/decoder/threading.c
+++ b/vp8/decoder/threading.c
@@ -50,9 +50,6 @@ static void setup_decoding_thread_data(VP8D_COMP *pbi, MACROBLOCKD *xd,
     mbd->subpixel_predict8x8 = xd->subpixel_predict8x8;
     mbd->subpixel_predict16x16 = xd->subpixel_predict16x16;
 
-    mbd->mode_info_context = pc->mi + pc->mode_info_stride * (i + 1);
-    mbd->mode_info_stride = pc->mode_info_stride;
-
     mbd->frame_type = pc->frame_type;
     mbd->pre = xd->pre;
     mbd->dst = xd->dst;
@@ -251,8 +248,8 @@ static void mt_decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd,
 
 static void mt_decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd,
                               int start_mb_row) {
-  volatile const int *last_row_current_mb_col;
-  volatile int *current_mb_col;
+  const int *last_row_current_mb_col;
+  int *current_mb_col;
   int mb_row;
   VP8_COMMON *pc = &pbi->common;
   const int nsync = pbi->sync_range;
@@ -289,6 +286,9 @@ static void mt_decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd,
 
   xd->up_available = (start_mb_row != 0);
 
+  xd->mode_info_context = pc->mi + pc->mode_info_stride * start_mb_row;
+  xd->mode_info_stride = pc->mode_info_stride;
+
   for (mb_row = start_mb_row; mb_row < pc->mb_rows;
        mb_row += (pbi->decoding_thread_count + 1)) {
     int recon_yoffset, recon_uvoffset;
@@ -355,14 +355,15 @@ static void mt_decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd,
                              xd->dst.uv_stride);
     }
 
-    for (mb_col = 0; mb_col < pc->mb_cols; mb_col++) {
-      *current_mb_col = mb_col - 1;
+    for (mb_col = 0; mb_col < pc->mb_cols; ++mb_col) {
+      if (((mb_col - 1) % nsync) == 0) {
+        pthread_mutex_t *mutex = &pbi->pmutex[mb_row];
+        protected_write(mutex, current_mb_col, mb_col - 1);
+      }
 
-      if ((mb_col & (nsync - 1)) == 0) {
-        while (mb_col > (*last_row_current_mb_col - nsync)) {
-          x86_pause_hint();
-          thread_sleep(0);
-        }
+      if (mb_row && !(mb_col & (nsync - 1))) {
+        pthread_mutex_t *mutex = &pbi->pmutex[mb_row - 1];
+        sync_read(mutex, mb_col, last_row_current_mb_col, nsync);
       }
 
       /* Distance of MB to the various image edges.
@@ -548,7 +549,7 @@ static void mt_decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd,
     }
 
     /* last MB of row is ready just after extension is done */
-    *current_mb_col = mb_col + nsync;
+    protected_write(&pbi->pmutex[mb_row], current_mb_col, mb_col + nsync);
 
     ++xd->mode_info_context; /* skip prediction column */
     xd->up_available = 1;
@@ -568,10 +569,10 @@ static THREAD_FUNCTION thread_decoding_proc(void *p_data) {
   ENTROPY_CONTEXT_PLANES mb_row_left_context;
 
   while (1) {
-    if (pbi->b_multithreaded_rd == 0) break;
+    if (protected_read(&pbi->mt_mutex, &pbi->b_multithreaded_rd) == 0) break;
 
     if (sem_wait(&pbi->h_event_start_decoding[ithread]) == 0) {
-      if (pbi->b_multithreaded_rd == 0) {
+      if (protected_read(&pbi->mt_mutex, &pbi->b_multithreaded_rd) == 0) {
         break;
       } else {
         MACROBLOCKD *xd = &mbrd->mbd;
@@ -591,6 +592,7 @@ void vp8_decoder_create_threads(VP8D_COMP *pbi) {
 
   pbi->b_multithreaded_rd = 0;
   pbi->allocated_decoding_thread_count = 0;
+  pthread_mutex_init(&pbi->mt_mutex, NULL);
 
   /* limit decoding threads to the max number of token partitions */
   core_count = (pbi->max_threads > 8) ? 8 : pbi->max_threads;
@@ -647,6 +649,16 @@ void vp8_decoder_create_threads(VP8D_COMP *pbi) {
 void vp8mt_de_alloc_temp_buffers(VP8D_COMP *pbi, int mb_rows) {
   int i;
 
+  /* De-allocate mutex */
+  if (pbi->pmutex != NULL) {
+    for (i = 0; i < mb_rows; ++i) {
+      pthread_mutex_destroy(&pbi->pmutex[i]);
+    }
+
+    vpx_free(pbi->pmutex);
+    pbi->pmutex = NULL;
+  }
+
   vpx_free(pbi->mt_current_mb_col);
   pbi->mt_current_mb_col = NULL;
 
@@ -712,7 +724,7 @@ void vp8mt_alloc_temp_buffers(VP8D_COMP *pbi, int width, int prev_mb_rows) {
   int i;
   int uv_width;
 
-  if (pbi->b_multithreaded_rd) {
+  if (protected_read(&pbi->mt_mutex, &pbi->b_multithreaded_rd)) {
     vp8mt_de_alloc_temp_buffers(pbi, prev_mb_rows);
 
     /* our internal buffers are always multiples of 16 */
@@ -730,6 +742,15 @@ void vp8mt_alloc_temp_buffers(VP8D_COMP *pbi, int width, int prev_mb_rows) {
 
     uv_width = width >> 1;
 
+    /* Allocate mutex */
+    CHECK_MEM_ERROR(pbi->pmutex,
+                    vpx_malloc(sizeof(*pbi->pmutex) * pc->mb_rows));
+    if (pbi->pmutex) {
+      for (i = 0; i < pc->mb_rows; ++i) {
+        pthread_mutex_init(&pbi->pmutex[i], NULL);
+      }
+    }
+
     /* Allocate an int for each mb row. */
     CALLOC_ARRAY(pbi->mt_current_mb_col, pc->mb_rows);
 
@@ -772,9 +793,9 @@ void vp8mt_alloc_temp_buffers(VP8D_COMP *pbi, int width, int prev_mb_rows) {
 
 void vp8_decoder_remove_threads(VP8D_COMP *pbi) {
   /* shutdown MB Decoding thread; */
-  if (pbi->b_multithreaded_rd) {
+  if (protected_read(&pbi->mt_mutex, &pbi->b_multithreaded_rd)) {
     int i;
-    pbi->b_multithreaded_rd = 0;
+    protected_write(&pbi->mt_mutex, &pbi->b_multithreaded_rd, 0);
 
     /* allow all threads to exit */
     for (i = 0; i < pbi->allocated_decoding_thread_count; ++i) {
@@ -804,6 +825,7 @@ void vp8_decoder_remove_threads(VP8D_COMP *pbi) {
 
     vp8mt_de_alloc_temp_buffers(pbi, pbi->common.mb_rows);
   }
+  pthread_mutex_destroy(&pbi->mt_mutex);
 }
 
 void vp8mt_decode_mb_rows(VP8D_COMP *pbi, MACROBLOCKD *xd) {