Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752797AbbKPJy3 (ORCPT ); Mon, 16 Nov 2015 04:54:29 -0500 Received: from mga09.intel.com ([134.134.136.24]:11385 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751917AbbKPJyO (ORCPT ); Mon, 16 Nov 2015 04:54:14 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,302,1444719600"; d="scan'208";a="851881503" Subject: Re: [PATCH 1/2] drm/i915: Break busywaiting for requests on pending signals To: Chris Wilson , Jens Axboe , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <1447594364-4206-1-git-send-email-chris@chris-wilson.co.uk> Cc: dri-devel@lists.freedesktop.org, Daniel Vetter , Eero Tamminen , "Rantala, Valtteri" , stable@kernel.vger.org From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <5649A7C2.90206@linux.intel.com> Date: Mon, 16 Nov 2015 09:54:10 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1447594364-4206-1-git-send-email-chris@chris-wilson.co.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3748 Lines: 102 Hi, On 15/11/15 13:32, Chris Wilson wrote: > The busywait in __i915_spin_request() does not respect pending signals > and so may consume the entire timeslice for the task instead of > returning to userspace to handle the signal. Obviously correct to break the spin, but if spending a jiffie to react to signals was the only problem then it is not too severe. Add something to the commit message about how it was found/reported and about the severity of impact, etc? Otherwise, Reviewed-by: Tvrtko Ursulin > Fixes regression from > commit 2def4ad99befa25775dd2f714fdd4d92faec6e34 [v4.2] > Author: Chris Wilson > Date: Tue Apr 7 16:20:41 2015 +0100 > > drm/i915: Optimistically spin for the request completion > > Signed-off-by: Chris Wilson > Cc: Jens Axboe > Cc; "Rogozhkin, Dmitry V" > Cc: Daniel Vetter > Cc: Tvrtko Ursulin > Cc: Eero Tamminen > Cc: "Rantala, Valtteri" > Cc: stable@kernel.vger.org > --- > drivers/gpu/drm/i915/i915_gem.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c > index 5cf4a1998273..740530c571d1 100644 > --- a/drivers/gpu/drm/i915/i915_gem.c > +++ b/drivers/gpu/drm/i915/i915_gem.c > @@ -1146,7 +1146,7 @@ static bool missed_irq(struct drm_i915_private *dev_priv, > return test_bit(ring->id, &dev_priv->gpu_error.missed_irq_rings); > } > > -static int __i915_spin_request(struct drm_i915_gem_request *req) > +static int __i915_spin_request(struct drm_i915_gem_request *req, int state) > { > unsigned long timeout; > > @@ -1158,6 +1158,9 @@ static int __i915_spin_request(struct drm_i915_gem_request *req) > if (i915_gem_request_completed(req, true)) > return 0; > > + if (signal_pending_state(state, current)) > + break; > + > if (time_after_eq(jiffies, timeout)) > break; > > @@ -1197,6 +1200,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, > struct drm_i915_private *dev_priv = dev->dev_private; > const bool irq_test_in_progress = > ACCESS_ONCE(dev_priv->gpu_error.test_irq_rings) & intel_ring_flag(ring); > + int state = interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE; > DEFINE_WAIT(wait); > unsigned long timeout_expire; > s64 before, now; > @@ -1221,7 +1225,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, > before = ktime_get_raw_ns(); > > /* Optimistic spin for the next jiffie before touching IRQs */ > - ret = __i915_spin_request(req); > + ret = __i915_spin_request(req, state); > if (ret == 0) > goto out; > > @@ -1233,8 +1237,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, > for (;;) { > struct timer_list timer; > > - prepare_to_wait(&ring->irq_queue, &wait, > - interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE); > + prepare_to_wait(&ring->irq_queue, &wait, state); > > /* We need to check whether any gpu reset happened in between > * the caller grabbing the seqno and now ... */ > @@ -1252,7 +1255,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req, > break; > } > > - if (interruptible && signal_pending(current)) { > + if (signal_pending_state(state, current)) { > ret = -ERESTARTSYS; > break; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/