From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: [PATCH] drm/i915: Fix timeout with missed interrupts in __wait_seqno Date: Thu, 12 Dec 2013 14:48:47 +0200 Message-ID: <20131212124847.GY10036@intel.com> References: <20131210121429.GD10793@nuc-i3427.alporthouse.com> <1386687763-21777-1-git-send-email-mika.kuoppala@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTP id 60077FA833 for ; Thu, 12 Dec 2013 04:48:54 -0800 (PST) Content-Disposition: inline In-Reply-To: <1386687763-21777-1-git-send-email-mika.kuoppala@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: Mika Kuoppala Cc: intel-gfx@lists.freedesktop.org, miku@iki.fi List-Id: intel-gfx@lists.freedesktop.org On Tue, Dec 10, 2013 at 05:02:43PM +0200, Mika Kuoppala wrote: > Commit 094f9a54e355 ("drm/i915: Fix __wait_seqno to use true infinite > timeouts") added support for __wait_seqno to detect missing interrupts and > go around them by polling. As there is also timeout detection in > __wait_seqno, the polling and timeout detection were done with the same > timer. > = > When there has been missed interrupts and polling is needed, the timer is > set to trigger in (now + 1) jiffies in future, instead of the caller > specified timeout. > = > Now when io_schedule() returns, we calculate the jiffies left to timeout > using the timer expiration value. As the current jiffies is now bound to = be > always equal or greater than the expiration value, the timeout_jiffies wi= ll > become zero or negative and we return -ETIME to caller even tho the > timeout was never reached. > = > Fix this by decoupling timeout calculation from timer expiration. > = > v2: Commit message with some sense in it (Chris Wilson) > = > v3: add parenthesis on timeout_expire calculation > = > v4: don't read jiffies without timeout (Chris Wilson) > = > Signed-off-by: Mika Kuoppala > --- > drivers/gpu/drm/i915/i915_gem.c | 14 ++++++-------- > 1 file changed, 6 insertions(+), 8 deletions(-) > = > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_= gem.c > index 92149bc..6d2e786 100644 > --- a/drivers/gpu/drm/i915/i915_gem.c > +++ b/drivers/gpu/drm/i915/i915_gem.c > @@ -1017,7 +1017,7 @@ static int __wait_seqno(struct intel_ring_buffer *r= ing, u32 seqno, > drm_i915_private_t *dev_priv =3D ring->dev->dev_private; > struct timespec before, now; > DEFINE_WAIT(wait); > - long timeout_jiffies; > + unsigned long timeout_expire; > int ret; > = > WARN(dev_priv->pc8.irqs_disabled, "IRQs disabled\n"); > @@ -1025,7 +1025,7 @@ static int __wait_seqno(struct intel_ring_buffer *r= ing, u32 seqno, > if (i915_seqno_passed(ring->get_seqno(ring, true), seqno)) > return 0; > = > - timeout_jiffies =3D timeout ? timespec_to_jiffies_timeout(timeout) : 1; > + timeout_expire =3D timeout ? jiffies + timespec_to_jiffies_timeout(time= out) : 0; > = > if (dev_priv->info->gen >=3D 6 && can_wait_boost(file_priv)) { > gen6_rps_boost(dev_priv); > @@ -1044,7 +1044,6 @@ static int __wait_seqno(struct intel_ring_buffer *r= ing, u32 seqno, > getrawmonotonic(&before); > for (;;) { > struct timer_list timer; > - unsigned long expire; > = > prepare_to_wait(&ring->irq_queue, &wait, > interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE); > @@ -1070,23 +1069,22 @@ static int __wait_seqno(struct intel_ring_buffer = *ring, u32 seqno, > break; > } > = > - if (timeout_jiffies <=3D 0) { > + if (timeout && time_after_eq(jiffies, timeout_expire)) { > ret =3D -ETIME; > break; > } > = > timer.function =3D NULL; > if (timeout || missed_irq(dev_priv, ring)) { > + unsigned long expire; > + > setup_timer_on_stack(&timer, fake_irq, (unsigned long)current); > - expire =3D jiffies + (missed_irq(dev_priv, ring) ? 1: timeout_jiffies= ); > + expire =3D missed_irq(dev_priv, ring) ? jiffies + 1 : timeout_expire; I guess we have very small race here if we get called w/ timeout=3D=3DNULL,= and missed_irq() was true above but is no longer true here. At that point we wo= uld set expire=3D0 and might end up waiting for quite a while. But that issue w= as present already in the code before this patch and otherwise it all looks good to me, so: Reviewed-by: Ville Syrj=E4l=E4 > mod_timer(&timer, expire); > } > = > io_schedule(); > = > - if (timeout) > - timeout_jiffies =3D expire - jiffies; > - > if (timer.function) { > del_singleshot_timer_sync(&timer); > destroy_timer_on_stack(&timer); > -- = > 1.7.9.5 > = > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- = Ville Syrj=E4l=E4 Intel OTC