Mesa (10.2): i965: Properly return *RESET* status in glGetGraphicsResetStatusARB

[Ian Romanick]

Module: Mesa
Branch: 10.2
Commit: 9a8f12ae034feefc7ce189485dfc8f387945eee0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=9a8f12ae034feefc7ce189485dfc8f387945eee0

Author: Pavel Popov <pavel.e.popov at intel.com>
Date:   Fri May 16 12:00:02 2014 +0700

i965: Properly return *RESET* status in glGetGraphicsResetStatusARB

The glGetGraphicsResetStatusARB from ARB_robustness extension always
returns GUILTY_CONTEXT_RESET_ARB and never returns NO_ERROR for guilty
context with LOSE_CONTEXT_ON_RESET_ARB strategy.  This is because Mesa
returns GUILTY_CONTEXT_RESET_ARB if batch_active !=0 whereas kernel
driver never reset batch_active and this variable always > 0 for guilty
context.  The same behaviour also can be observed for batch_pending and
INNOCENT_CONTEXT_RESET_ARB.

But ARB_robustness spec says:

  If a reset status other than NO_ERROR is returned and subsequent calls
  return NO_ERROR, the context reset was encountered and completed. If a
  reset status is repeatedly returned, the context may be in the process
  of resetting.

  8. How should the application react to a reset context event?
  RESOLVED: For this extension, the application is expected to query the
  reset status until NO_ERROR is returned. If a reset is encountered, at
  least one *RESET* status will be returned. Once NO_ERROR is
  encountered, the application can safely destroy the old context and
  create a new one.

The main problem is the context may be in the process of resetting and
in this case a reset status should be repeatedly returned.  But looks
like the kernel driver returns nonzero active/pending only if the
context reset has already been encountered and completed.  For this
reason the *RESET* status cannot be repeatedly returned and should be
returned only once.

The reset_count and brw->reset_count variables can be used to control
that glGetGraphicsResetStatusARB returns *RESET* status only once for
each context.  Note the i915 triggers reset_count twice which allows to
return correct reset count immediately after active/pending have been
incremented.

v2 (idr): Trivial reformatting of comments.

Signed-off-by: Pavel Popov <pavel.e.popov at intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
Cc: "10.1 10.2" <mesa-stable at lists.freedesktop.org>
(cherry picked from commit 8dc4a98c44a824630f3cc234136833dbac9a1f4c)

---

 src/mesa/drivers/dri/i965/brw_reset.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_reset.c b/src/mesa/drivers/dri/i965/brw_reset.c
index 7eca1bc..e3182b1 100644
--- a/src/mesa/drivers/dri/i965/brw_reset.c
+++ b/src/mesa/drivers/dri/i965/brw_reset.c
@@ -42,6 +42,13 @@ brw_get_graphics_reset_status(struct gl_context *ctx)
     */
    assert(brw->hw_ctx != NULL);
 
+   /* A reset status other than NO_ERROR was returned last time. I915 returns
+    * nonzero active/pending only if reset has been encountered and completed.
+    * Return NO_ERROR from now on.
+    */
+   if (brw->reset_count != 0)
+      return GL_NO_ERROR;
+
    err = drm_intel_get_reset_stats(brw->hw_ctx, &reset_count, &active,
                                    &pending);
    if (err)
@@ -50,18 +57,19 @@ brw_get_graphics_reset_status(struct gl_context *ctx)
    /* A reset was observed while a batch from this context was executing.
     * Assume that this context was at fault.
     */
-   if (active != 0)
+   if (active != 0) {
+      brw->reset_count = reset_count;
       return GL_GUILTY_CONTEXT_RESET_ARB;
+   }
 
    /* A reset was observed while a batch from this context was in progress,
     * but the batch was not executing.  In this case, assume that the context
     * was not at fault.
     */
-   if (pending != 0)
+   if (pending != 0) {
+      brw->reset_count = reset_count;
       return GL_INNOCENT_CONTEXT_RESET_ARB;
-
-   /* FINISHME: Should we report anything if reset_count > brw->reset_count?
-    */
+   }
 
    return GL_NO_ERROR;
 }