dri3_crash_fix.patch

   1 Upon reception of an event that lowered the number of active back buffers,
   2 the code would immediately try to free all back buffers with an id equal to or
   3 higher than the new number of active back buffers.
   4
   5 However, that could lead to an active or to-be-active back buffer being freed,
   6 since the old number of back buffers was used when obtaining an idle back
   7 buffer for use.
   8
   9 This lead to crashes when lowering the number of active back buffers by
  10 transitioning from page-flipping to non-page-flipping presents.
  11
  12 Fix this by computing the number of active back buffers only when trying to
  13 obtain a new back buffer.
  14
  15 Fixes: 15e208c4cc ("loader/dri3: Don't accidently free buffer holding new back content")
  16 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104214
  17 Cc: "17.3" <mesa-stable@lists.freedesktop.org>
  18 Tested-by: Andriy.Khulap <andriy.khulap@globallogic.com>
  19 Tested-by: Vadym Shovkoplias <vadym.shovkoplias@globallogic.com>
  20 Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
  21 Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
  22 ---
  23  src/loader/loader_dri3_helper.c | 6 +++---
  24  1 file changed, 3 insertions(+), 3 deletions(-)
  25
  26 diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
  27 index cc890bc..8f8efcb 100644
  28 --- a/src/loader/loader_dri3_helper.c
  29 +++ b/src/loader/loader_dri3_helper.c
  30 @@ -205,7 +205,6 @@ void
  31  loader_dri3_set_swap_interval(struct loader_dri3_drawable *draw, int interval)
  32  {
  33     draw->swap_interval = interval;
  34 -   dri3_update_num_back(draw);
  35  }
  36
  37  /** dri3_free_render_buffer
  38 @@ -377,7 +376,6 @@ dri3_handle_present_event(struct loader_dri3_drawable *draw,
  39              draw->flipping = false;
  40              break;
  41           }
  42 -         dri3_update_num_back(draw);
  43
  44           if (draw->vtable->show_fps)
  45              draw->vtable->show_fps(draw, ce->ust);
  46 @@ -402,7 +400,8 @@ dri3_handle_present_event(struct loader_dri3_drawable *draw,
  47              buf->busy = 0;
  48
  49           if (buf && draw->num_back <= b && b < LOADER_DRI3_MAX_BACK &&
  50 -             draw->cur_blit_source != b) {
  51 +             draw->cur_blit_source != b &&
  52 +             !buf->busy) {
  53              dri3_free_render_buffer(draw, buf);
  54              draw->buffers[b] = NULL;
  55           }
  56 @@ -537,6 +536,7 @@ dri3_find_back(struct loader_dri3_drawable *draw)
  57     /* Check whether we need to reuse the current back buffer as new back.
  58      * In that case, wait until it's not busy anymore.
  59      */
  60 +   dri3_update_num_back(draw);
  61     num_to_consider = draw->num_back;
  62     if (!loader_dri3_have_image_blit(draw) && draw->cur_blit_source != -1) {
  63        num_to_consider = 1;
  64