i965: share buffer managers across screens

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: <mesa-stable@lists.freedesktop.org>
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1373
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4086>

src/mesa/drivers/dri/i965/brw_bufmgr.c

@@ -136,6 +136,10 @@ struct bo_cache_bucket {
 };
 
 struct brw_bufmgr {
+   uint32_t refcount;
+
+   struct list_head link;
+
    int fd;
 
    mtx_t lock;
@@ -157,6 +161,12 @@ struct brw_bufmgr {
    uint64_t initial_kflags;
 };
 
+static mtx_t global_bufmgr_list_mutex = _MTX_INITIALIZER_NP;
+static struct list_head global_bufmgr_list = {
+   .next = &global_bufmgr_list,
+   .prev = &global_bufmgr_list,
+};
+
 static int bo_set_tiling_internal(struct brw_bo *bo, uint32_t tiling_mode,
                                   uint32_t stride);
 
@@ -1279,8 +1289,19 @@ brw_bo_wait(struct brw_bo *bo, int64_t timeout_ns)
 }
 
 void
-brw_bufmgr_destroy(struct brw_bufmgr *bufmgr)
+brw_bufmgr_unref(struct brw_bufmgr *bufmgr)
 {
+   mtx_lock(&global_bufmgr_list_mutex);
+   if (p_atomic_dec_zero(&bufmgr->refcount)) {
+      list_del(&bufmgr->link);
+   } else {
+      bufmgr = NULL;
+   }
+   mtx_unlock(&global_bufmgr_list_mutex);
+
+   if (!bufmgr)
+      return;
+
    mtx_destroy(&bufmgr->lock);
 
    /* Free any cached buffer objects we were going to reuse */
@@ -1309,6 +1330,9 @@ brw_bufmgr_destroy(struct brw_bufmgr *bufmgr)
       }
    }
 
+   close(bufmgr->fd);
+   bufmgr->fd = -1;
+
    free(bufmgr);
 }
 
@@ -1651,14 +1675,21 @@ brw_using_softpin(struct brw_bufmgr *bufmgr)
    return bufmgr->initial_kflags & EXEC_OBJECT_PINNED;
 }
 
+static struct brw_bufmgr *
+brw_bufmgr_ref(struct brw_bufmgr *bufmgr)
+{
+   p_atomic_inc(&bufmgr->refcount);
+   return bufmgr;
+}
+
 /**
  * Initializes the GEM buffer manager, which uses the kernel to allocate, map,
  * and manage map buffer objections.
  *
  * \param fd File descriptor of the opened DRM device.
  */
-struct brw_bufmgr *
+static struct brw_bufmgr *
-brw_bufmgr_init(struct gen_device_info *devinfo, int fd, bool bo_reuse)
+brw_bufmgr_create(struct gen_device_info *devinfo, int fd, bool bo_reuse)
 {
    struct brw_bufmgr *bufmgr;
 
@@ -1675,9 +1706,16 @@ brw_bufmgr_init(struct gen_device_info *devinfo, int fd, bool bo_reuse)
     * Don't do this! Ensure that each library/bufmgr has its own device
     * fd so that its namespace does not clash with another.
     */
-   bufmgr->fd = fd;
+   bufmgr->fd = dup(fd);
+   if (bufmgr->fd < 0) {
+      free(bufmgr);
+      return NULL;
+   }
+
+   p_atomic_set(&bufmgr->refcount, 1);
 
    if (mtx_init(&bufmgr->lock, mtx_plain) != 0) {
+      close(bufmgr->fd);
       free(bufmgr);
       return NULL;
    }
@@ -1719,6 +1757,7 @@ brw_bufmgr_init(struct gen_device_info *devinfo, int fd, bool bo_reuse)
           * might actually mean requiring 4.14.
           */
          fprintf(stderr, "i965 requires softpin (Kernel 4.5) on Gen10+.");
+         close(bufmgr->fd);
          free(bufmgr);
          return NULL;
       }
@@ -1733,3 +1772,41 @@ brw_bufmgr_init(struct gen_device_info *devinfo, int fd, bool bo_reuse)
 
    return bufmgr;
 }
+
+struct brw_bufmgr *
+brw_bufmgr_get_for_fd(struct gen_device_info *devinfo, int fd, bool bo_reuse)
+{
+   struct stat st;
+
+   if (fstat(fd, &st))
+      return NULL;
+
+   struct brw_bufmgr *bufmgr = NULL;
+
+   mtx_lock(&global_bufmgr_list_mutex);
+   list_for_each_entry(struct brw_bufmgr, iter_bufmgr, &global_bufmgr_list, link) {
+      struct stat iter_st;
+      if (fstat(iter_bufmgr->fd, &iter_st))
+         continue;
+
+      if (st.st_rdev == iter_st.st_rdev) {
+         assert(iter_bufmgr->bo_reuse == bo_reuse);
+         bufmgr = brw_bufmgr_ref(iter_bufmgr);
+         goto unlock;
+      }
+   }
+
+   bufmgr = brw_bufmgr_create(devinfo, fd, bo_reuse);
+   list_addtail(&bufmgr->link, &global_bufmgr_list);
+
+ unlock:
+   mtx_unlock(&global_bufmgr_list_mutex);
+
+   return bufmgr;
+}
+
+int
+brw_bufmgr_get_fd(struct brw_bufmgr *bufmgr)
+{
+   return bufmgr->fd;
+}

src/mesa/drivers/dri/i965/brw_bufmgr.h

@@ -300,9 +300,9 @@ int brw_bo_subdata(struct brw_bo *bo, uint64_t offset,
 void brw_bo_wait_rendering(struct brw_bo *bo);
 
 /**
- * Tears down the buffer manager instance.
+ * Unref a buffer manager instance.
  */
-void brw_bufmgr_destroy(struct brw_bufmgr *bufmgr);
+void brw_bufmgr_unref(struct brw_bufmgr *bufmgr);
 
 /**
  * Get the current tiling (and resulting swizzling) mode for the bo.
@@ -343,8 +343,9 @@ int brw_bo_busy(struct brw_bo *bo);
 int brw_bo_madvise(struct brw_bo *bo, int madv);
 
 /* drm_bacon_bufmgr_gem.c */
-struct brw_bufmgr *brw_bufmgr_init(struct gen_device_info *devinfo, int fd,
+struct brw_bufmgr *brw_bufmgr_get_for_fd(struct gen_device_info *devinfo, int fd,
-                                   bool bo_reuse);
+                                         bool bo_reuse);
+
 struct brw_bo *brw_bo_gem_create_from_name(struct brw_bufmgr *bufmgr,
                                            const char *name,
                                            unsigned int handle);
@@ -359,6 +360,8 @@ int brw_hw_context_set_priority(struct brw_bufmgr *bufmgr,
 
 void brw_destroy_hw_context(struct brw_bufmgr *bufmgr, uint32_t ctx_id);
 
+int brw_bufmgr_get_fd(struct brw_bufmgr *bufmgr);
+
 int brw_bo_gem_export_to_prime(struct brw_bo *bo, int *prime_fd);
 struct brw_bo *brw_bo_gem_create_from_prime(struct brw_bufmgr *bufmgr,
                                             int prime_fd);

src/mesa/drivers/dri/i965/intel_screen.c

@@ -1707,7 +1707,7 @@ intelDestroyScreen(__DRIscreen * sPriv)
 {
    struct intel_screen *screen = sPriv->driverPrivate;
 
-   brw_bufmgr_destroy(screen->bufmgr);
+   brw_bufmgr_unref(screen->bufmgr);
    driDestroyOptionInfo(&screen->optionCache);
 
    disk_cache_destroy(screen->disk_cache);
@@ -1910,6 +1910,8 @@ err_out:
 static bool
 intel_init_bufmgr(struct intel_screen *screen)
 {
+   __DRIscreen *dri_screen = screen->driScrnPriv;
+
    if (getenv("INTEL_NO_HW") != NULL)
       screen->no_hw = true;
 
@@ -1923,12 +1925,13 @@ intel_init_bufmgr(struct intel_screen *screen)
       break;
    }
 
-   screen->bufmgr = brw_bufmgr_init(&screen->devinfo, screen->fd, bo_reuse);
+   screen->bufmgr = brw_bufmgr_get_for_fd(&screen->devinfo, dri_screen->fd, bo_reuse);
    if (screen->bufmgr == NULL) {
       fprintf(stderr, "[%s:%u] Error initializing buffer manager.\n",
 	      __func__, __LINE__);
       return false;
    }
+   screen->fd = brw_bufmgr_get_fd(screen->bufmgr);
 
    if (!intel_get_boolean(screen, I915_PARAM_HAS_EXEC_NO_RELOC)) {
       fprintf(stderr, "[%s: %u] Kernel 3.9 required.\n", __func__, __LINE__);
@@ -2561,7 +2564,6 @@ __DRIconfig **intelInitScreen2(__DRIscreen *dri_screen)
       return NULL;
    }
 
-   screen->fd = dri_screen->fd;
    if (!intel_init_bufmgr(screen))
        return NULL;