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    Subject[PATCH 3.13 168/259] drm/i915: Reorder the semaphore deadlock check, again
    Date
    3.13.11.6 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Chris Wilson <chris@chris-wilson.co.uk>

    commit a0d036b074b4a5a933e37fcb9bdd6b3cc80a0387 upstream.

    commit 4be173813e57c7298103a83155c2391b5b167b4c
    Author: Chris Wilson <chris@chris-wilson.co.uk>
    Date: Fri Jun 6 10:22:29 2014 +0100

    drm/i915: Reorder semaphore deadlock check

    did the majority of the work, but it missed one crucial detail:

    The check for the unkickable deadlock on this ring must come after the
    check whether the ring that we are waiting on has already passed its
    target seqno.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80709
    Tested-by: Stefan Huber <shuber@sthu.org>
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Mika Kuoppala <mika.kuoppala@intel.com>
    Cc: Jani Nikula <jani.nikula@intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    drivers/gpu/drm/i915/i915_irq.c | 11 ++++-------
    1 file changed, 4 insertions(+), 7 deletions(-)

    diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
    index 2093c72..3a10da2 100644
    --- a/drivers/gpu/drm/i915/i915_irq.c
    +++ b/drivers/gpu/drm/i915/i915_irq.c
    @@ -2392,7 +2392,7 @@ static int semaphore_passed(struct intel_ring_buffer *ring)
    {
    struct drm_i915_private *dev_priv = ring->dev->dev_private;
    struct intel_ring_buffer *signaller;
    - u32 seqno, ctl;
    + u32 seqno;

    ring->hangcheck.deadlock++;

    @@ -2404,15 +2404,12 @@ static int semaphore_passed(struct intel_ring_buffer *ring)
    if (signaller->hangcheck.deadlock >= I915_NUM_RINGS)
    return -1;

    - /* cursory check for an unkickable deadlock */
    - ctl = I915_READ_CTL(signaller);
    - if (ctl & RING_WAIT_SEMAPHORE && semaphore_passed(signaller) < 0)
    - return -1;
    -
    if (i915_seqno_passed(signaller->get_seqno(signaller, false), seqno))
    return 1;

    - if (signaller->hangcheck.deadlock)
    + /* cursory check for an unkickable deadlock */
    + if (I915_READ_CTL(signaller) & RING_WAIT_SEMAPHORE &&
    + semaphore_passed(signaller) < 0)
    return -1;

    return 0;
    --
    1.9.1


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