• Chris Wilson's avatar
    drm/i915: Break modeset deadlocks on reset · 36703e79
    Chris Wilson authored
    Trying to do a modeset from within a reset is fraught with danger. We
    can fall into a cyclic deadlock where the modeset is waiting on a
    previous modeset that is waiting on a request, and since the GPU hung
    that request completion is waiting on the reset. As modesetting doesn't
    allow its locks to be broken and restarted, or for its *own* reset
    mechanism to take over the display, we have to do something very
    evil instead. If we detect that we are stuck waiting to prepare the
    display reset (by using a very simple timeout), resort to cancelling all
    in-flight requests and throwing the user data into /dev/null, which is
    marginally better than the driver locking up and keeping that data to
    itself.
    
    This is not a fix; this is just a workaround that unbreaks machines
    until we can resolve the deadlock in a way that doesn't lose data!
    
    v2: Move the retirement from set-wegded to the i915_reset() error path,
    after which we no longer any delayed worker cleanup for
    i915_handle_error()
    v3: C abuse for syntactic sugar
    v4: Cover all waits with the timeout to catch more driver breakage
    
    References: https://bugs.freedesktop.org/show_bug.cgi?id=99093Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
    Cc: Mika Kuoppala <mika.kuoppala@intel.com>
    Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
    Link: http://patchwork.freedesktop.org/patch/msgid/20170622105625.16952-1-chris@chris-wilson.co.ukReviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
    36703e79
i915_drv.c 77.9 KB