aboutsummaryrefslogtreecommitdiff
path: root/drivers
diff options
context:
space:
mode:
authorDaniel Vetter2011-09-08 14:00:21 +0200
committerKeith Packard2011-10-20 14:11:17 -0700
commita9e2641dee52cae2db7688a749344365642a5e79 (patch)
tree55db91e129c293ab51f55702118abff2105edee0 /drivers
parent4fb066ab9ef3111c86d9fb8f13f1178885cf7f1c (diff)
drm/i915: close PM interrupt masking races in the rps work func
This patch closes the following race: We get a PM interrupt A, mask it, set dev_priv->iir = PM_A and kick of the work item. Scheduler isn't grumpy, so the work queue takes rps_lock, grabs pm_iir = dev_priv->pm_iir and pm_imr = READ(PMIMR). Note that pm_imr == pm_iir because we've just masked the interrupt we've got. Now hw sends out PM interrupt B (not masked), we process it and mask it. Later on the irq handler also clears PMIIR. Then the work item proceeds and at the end clears PMIMR. Because (local) pm_imr == pm_iir we have pm_imr & ~pm_iir == 0 so all interrupts are enabled. Hardware is still interrupt-happy, and sends out a new PM interrupt B. PMIMR doesn't mask B (it does not mask anything), PMIIR is cleared, so we get it and hit the WARN in the interrupt handler (because dev_priv->pm_iir == PM_B). That's why I've moved the WRITE(PMIMR, 0) up under the protection of the rps_lock. And write an uncoditional 0 to PMIMR, because that's what we'll do anyway. This races looks much more likely because we can arbitrarily extend the window by grabing dev->struct mutex right after the irq handler has processed the first PM_B interrupt. Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Ben Widawsky <ben@bwidawsk.net> Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpu/drm/i915/i915_irq.c2
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 98eedddc7440..9ee2729fe5c6 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -383,6 +383,7 @@ static void gen6_pm_rps_work(struct work_struct *work)
pm_iir = dev_priv->pm_iir;
dev_priv->pm_iir = 0;
pm_imr = I915_READ(GEN6_PMIMR);
+ I915_WRITE(GEN6_PMIMR, 0);
spin_unlock_irq(&dev_priv->rps_lock);
if (!pm_iir)
@@ -420,7 +421,6 @@ static void gen6_pm_rps_work(struct work_struct *work)
* an *extremely* unlikely race with gen6_rps_enable() that is prevented
* by holding struct_mutex for the duration of the write.
*/
- I915_WRITE(GEN6_PMIMR, pm_imr & ~pm_iir);
mutex_unlock(&dev_priv->dev->struct_mutex);
}