[Bug 78769] i965: glGetGraphicsResetStatusARB always returns GUILTY_CONTEXT_RESET_ARB status for guilty context

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=78769

Ian Romanick <idr at freedesktop.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Ian Romanick <idr at freedesktop.org> ---
Fixed on master by the commit below.  This has been cherry picked to the 10.2
branch as 9a8f12ae, and it will be included in 10.2-rc3.

commit 8dc4a98c44a824630f3cc234136833dbac9a1f4c
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>

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