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From: Ben Widawsky <ben@bwidawsk.net>
To: intel-gfx@lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, Ben Widawsky <ben@bwidawsk.net>
Subject: [PATCH] drm/i915: Fix rps irq warning
Date: Sat,  3 Sep 2011 20:24:15 -0700
Message-ID: <1315106655-26782-1-git-send-email-ben@bwidawsk.net> (raw)

I couldn't reproduce this one, but...  Interrupt mask state is lost if
three interrupts occur before the workqueue has run.

Should be straight forward to reproduce even without SMP. I'm pretty
sure Dan Vetter was trying to explain this to me, and I couldn't get it.
My solution I think is different than his though.

Here is a sample failure:
  <pm irq 1<<0 occurs>
  local iir = 1
  spin lock
  mask_pm_irq(1 << 0);
  dev_priv->iir = 1;
  spin_unlock
  clear_pm_irq(1 << 0);

  <pm irq 1 << 1 occurs>
  local iir = 2
  spin lock
  mask_pm_irq(1 << 1); // here is the bug
  dev_priv->iir = 3;
  clear_pm_irq(1 << 1);

  <pm irq 1 << 0 occurs again>
  local iir = 1
  spin lock
  WARN!!!

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_irq.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 9cbb0cd..55518e3 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -649,8 +649,8 @@ static irqreturn_t ironlake_irq_handler(DRM_IRQ_ARGS)
 		unsigned long flags;
 		spin_lock_irqsave(&dev_priv->rps_lock, flags);
 		WARN(dev_priv->pm_iir & pm_iir, "Missed a PM interrupt\n");
-		I915_WRITE(GEN6_PMIMR, pm_iir);
 		dev_priv->pm_iir |= pm_iir;
+		I915_WRITE(GEN6_PMIMR, dev_priv->pm_iir);
 		spin_unlock_irqrestore(&dev_priv->rps_lock, flags);
 		queue_work(dev_priv->wq, &dev_priv->rps_work);
 	}
-- 
1.7.6.1

             reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-04  3:24 Ben Widawsky [this message]
2011-09-04  9:03 ` Chris Wilson
2011-09-04 15:49   ` Ben Widawsky
2011-09-04 15:34     ` [PATCH 0/3] slaughter rps races some more Daniel Vetter
2011-09-04 15:35       ` [PATCH 1/3] drm/i915: close PM interrupt masking races in the irq handler Daniel Vetter
2011-09-04 17:09         ` Ben Widawsky
2011-09-04 15:35       ` [PATCH 2/3] drm/i915: close PM interrupt masking races in the rps work func Daniel Vetter
2011-09-04 17:08         ` Ben Widawsky
2011-09-04 19:26           ` Daniel Vetter
2011-09-04 19:56             ` Ben Widawsky
2011-09-04 20:10               ` Daniel Vetter
2011-09-04 21:38                 ` Ben Widawsky
2011-09-05  6:38                   ` Daniel Vetter
2011-09-05  6:51                     ` Ben Widawsky
2011-09-05 12:15                       ` Chris Wilson
2011-09-04 15:35       ` [PATCH 3/3] drm/i915: close rps work vs. rps disable races Daniel Vetter
2011-09-04 17:23         ` Ben Widawsky
2011-09-04 19:17           ` Daniel Vetter
2011-09-04 19:50             ` Ben Widawsky
2011-09-04 19:57               ` Daniel Vetter
2011-09-05  8:15                 ` [PATCH] drm/i915: properly cancel rps_work on module unload Daniel Vetter
2011-09-05 17:27                   ` Ben Widawsky

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