Mesa (master): i965: Discard bo->map_count

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: c913241458be85fd5382d07a918a8e876296a3b6
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=c913241458be85fd5382d07a918a8e876296a3b6

Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Jun 20 11:57:34 2017 +0100

i965: Discard bo->map_count

Supposedly we were keeping a reference count for the number of users of
a mapping so that we could use valgrind to detect access to the map
outside of the valid section. However, we were incrementing the counter
only when first creating the cached mapping but decrementing on every
unmap. The bo->map_count tracking was wrong and so the debugging code
was completely useless.

v2 (Ken): Separate out atomic compare and swap optimization.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Matt Turner <mattst88 at gmail.com>

---

 src/mesa/drivers/dri/i965/brw_bufmgr.c | 55 ++--------------------------------
 src/mesa/drivers/dri/i965/brw_bufmgr.h |  1 -
 2 files changed, 3 insertions(+), 53 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/i965/brw_bufmgr.c
index abd0722ba6..9e67efa4d3 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
@@ -546,21 +546,6 @@ bo_free(struct brw_bo *bo)
    free(bo);
 }
 
-static void
-bo_mark_mmaps_incoherent(struct brw_bo *bo)
-{
-#if HAVE_VALGRIND
-   if (bo->map_cpu)
-      VALGRIND_MAKE_MEM_NOACCESS(bo->map_cpu, bo->size);
-
-   if (bo->map_wc)
-      VALGRIND_MAKE_MEM_NOACCESS(bo->map_wc, bo->size);
-
-   if (bo->map_gtt)
-      VALGRIND_MAKE_MEM_NOACCESS(bo->map_gtt, bo->size);
-#endif
-}
-
 /** Frees all cached buffers significantly older than @time. */
 static void
 cleanup_bo_cache(struct brw_bufmgr *bufmgr, time_t time)
@@ -594,13 +579,6 @@ bo_unreference_final(struct brw_bo *bo, time_t time)
 
    DBG("bo_unreference final: %d (%s)\n", bo->gem_handle, bo->name);
 
-   /* Clear any left-over mappings */
-   if (bo->map_count) {
-      DBG("bo freed with non-zero map-count %d\n", bo->map_count);
-      bo->map_count = 0;
-      bo_mark_mmaps_incoherent(bo);
-   }
-
    bucket = bucket_for_size(bufmgr, bo->size);
    /* Put the buffer into our internal cache for reuse if we can. */
    if (bufmgr->bo_reuse && bo->reusable && bucket != NULL &&
@@ -677,8 +655,7 @@ brw_bo_map_cpu(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
    if (!bo->map_cpu) {
       struct drm_i915_gem_mmap mmap_arg;
 
-      DBG("brw_bo_map_cpu: %d (%s), map_count=%d\n",
-          bo->gem_handle, bo->name, bo->map_count);
+      DBG("brw_bo_map_cpu: %d (%s)\n", bo->gem_handle, bo->name);
 
       memclear(mmap_arg);
       mmap_arg.handle = bo->gem_handle;
@@ -691,7 +668,6 @@ brw_bo_map_cpu(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
          pthread_mutex_unlock(&bufmgr->lock);
          return NULL;
       }
-      bo->map_count++;
       VG(VALGRIND_MALLOCLIKE_BLOCK(mmap_arg.addr_ptr, mmap_arg.size, 0, 1));
       bo->map_cpu = (void *) (uintptr_t) mmap_arg.addr_ptr;
    }
@@ -703,8 +679,6 @@ brw_bo_map_cpu(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
                  flags & MAP_WRITE ? I915_GEM_DOMAIN_CPU : 0);
    }
 
-   bo_mark_mmaps_incoherent(bo);
-   VG(VALGRIND_MAKE_MEM_DEFINED(bo->map_cpu, bo->size));
    pthread_mutex_unlock(&bufmgr->lock);
 
    return bo->map_cpu;
@@ -721,8 +695,7 @@ brw_bo_map_gtt(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
    if (bo->map_gtt == NULL) {
       struct drm_i915_gem_mmap_gtt mmap_arg;
 
-      DBG("bo_map_gtt: mmap %d (%s), map_count=%d\n",
-          bo->gem_handle, bo->name, bo->map_count);
+      DBG("bo_map_gtt: mmap %d (%s)\n", bo->gem_handle, bo->name);
 
       memclear(mmap_arg);
       mmap_arg.handle = bo->gem_handle;
@@ -748,7 +721,6 @@ brw_bo_map_gtt(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
          pthread_mutex_unlock(&bufmgr->lock);
          return NULL;
       }
-      bo->map_count++;
    }
 
    DBG("bo_map_gtt: %d (%s) -> %p\n", bo->gem_handle, bo->name,
@@ -759,8 +731,6 @@ brw_bo_map_gtt(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
                  I915_GEM_DOMAIN_GTT, I915_GEM_DOMAIN_GTT);
    }
 
-   bo_mark_mmaps_incoherent(bo);
-   VG(VALGRIND_MAKE_MEM_DEFINED(bo->map_gtt, bo->size));
    pthread_mutex_unlock(&bufmgr->lock);
 
    return bo->map_gtt;
@@ -795,26 +765,7 @@ brw_bo_map(struct brw_context *brw, struct brw_bo *bo, unsigned flags)
 int
 brw_bo_unmap(struct brw_bo *bo)
 {
-   struct brw_bufmgr *bufmgr = bo->bufmgr;
-   int ret = 0;
-
-   pthread_mutex_lock(&bufmgr->lock);
-
-   if (bo->map_count <= 0) {
-      DBG("attempted to unmap an unmapped bo\n");
-      pthread_mutex_unlock(&bufmgr->lock);
-      /* Preserve the old behaviour of just treating this as a
-       * no-op rather than reporting the error.
-       */
-      return 0;
-   }
-
-   if (--bo->map_count == 0) {
-      bo_mark_mmaps_incoherent(bo);
-   }
-   pthread_mutex_unlock(&bufmgr->lock);
-
-   return ret;
+   return 0;
 }
 
 int
diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.h b/src/mesa/drivers/dri/i965/brw_bufmgr.h
index 48488bc33b..6482abd09a 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.h
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.h
@@ -114,7 +114,6 @@ struct brw_bo {
    void *map_gtt;
    /** WC CPU address for the buffer, saved across map/unmap cycles */
    void *map_wc;
-   int map_count;
 
    /** BO cache list */
    struct list_head head;