Hi, On 27-07-17 16:35, Imre Deak wrote:
Hi, On Thu, Jul 06, 2017 at 09:24:47PM +0200, Hans de Goede wrote:assert_rpm_wakelock_held is triggered from i915_pmic_bus_access_notifier even though it gets unregistered on (runtime) suspend, this is caused by a race happening under the following circumstances: intel_runtime_pm_put does: atomic_dec(&dev_priv->pm.wakeref_count); pm_runtime_mark_last_busy(kdev); pm_runtime_put_autosuspend(kdev); And pm_runtime_put_autosuspend calls intel_runtime_suspend from a workqueue, so there is ample of time between the atomic_dec() and intel_runtime_suspend() unregistering the notifier. If the notifier gets called in this windowd assert_rpm_wakelock_held falsely triggers (at this point we're not runtime-suspended yet). This commit adds disable_rpm_wakeref_asserts and enable_rpm_wakeref_asserts calls around the intel_uncore_forcewake_get(FORCEWAKE_ALL) call in i915_pmic_bus_access_notifier fixing the false-positive WARN_ON. Reported-by: FKr <bugs-freedesktop@xxxxxxxxxxx> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- Changes in v2: -Rebase on current (July 6th 2017) drm-next --- drivers/gpu/drm/i915/intel_uncore.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c index 9882724bc2b6..168b28a87f76 100644 --- a/drivers/gpu/drm/i915/intel_uncore.c +++ b/drivers/gpu/drm/i915/intel_uncore.c @@ -1171,8 +1171,15 @@ static int i915_pmic_bus_access_notifier(struct notifier_block *nb, * bus, which will be busy after this notification, leading to: * "render: timed out waiting for forcewake ack request." * errors. + * + * This notifier may get called between intel_runtime_pm_put() + * doing atomic_dec(wakeref_count) and intel_runtime_resume() + * unregistering this notifier, which leads to false-positive + * assert_rpm_wakelock_held() triggering.the following would describe better the reason for disabling wakeref asserts. That is we access the HW without holding a runtime PM reference, but it's ok here since it's handled as a special case during runtime suspend: * The notifier is unregistered during intel_runtime_suspend(), * so it's ok to access the HW here without holding an RPM * wake reference -> disable wakeref asserts for the time of * the access. With that this looks ok: Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
Thank you for the review, unfortunately I've been a bit swamped with other stuff. But I'm catching up now. I've made the suggest change to the comment and added your Reviewed-by for the upcoming v3 of this patch. Regards, Hans
*/ + disable_rpm_wakeref_asserts(dev_priv); intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL); + enable_rpm_wakeref_asserts(dev_priv); break; case MBI_PMIC_BUS_ACCESS_END: intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL); -- 2.13.0
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