* linux-next: build failure after merge of the tip tree (from the drm-intel tree)
@ 2016-07-05 3:53 Stephen Rothwell
2016-07-05 8:25 ` Peter Zijlstra
0 siblings, 1 reply; 3+ messages in thread
From: Stephen Rothwell @ 2016-07-05 3:53 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Peter Zijlstra,
Daniel Vetter, intel-gfx, dri-devel
Cc: linux-next, linux-kernel, Chris Wilson
Hi all,
After merging the tip tree, today's linux-next build (x86_64 allmodconfig)
failed like this:
In file included from include/uapi/linux/stddef.h:1:0,
from include/linux/stddef.h:4,
from include/uapi/linux/posix_types.h:4,
from include/uapi/linux/types.h:13,
from include/linux/types.h:5,
from include/linux/sysrq.h:18,
from drivers/gpu/drm/i915/i915_irq.c:31:
drivers/gpu/drm/i915/i915_irq.c: In function 'i915_hangcheck_elapsed':
include/linux/compiler.h:542:50: error: incompatible types when initializing type 'const void * const' using type 'bool {aka _Bool}'
__maybe_unused const void * const _________p2 = _________p1; \
^
drivers/gpu/drm/i915/i915_irq.c:3098:7: note: in expansion of macro 'lockless_dereference'
if (!lockless_dereference(dev_priv->gt.awake))
^
Caused by commit
67d97da34917 ("drm/i915: Only start retire worker when idle")
from the drm-intel tree interacting with commit
331b6d8c7afc ("locking/barriers: Validate lockless_dereference() is used on a pointer type")
from the tip tree.
>From include/linux/compiler.h:
* lockless_dereference() - safely load a pointer for later dereference
* @p: The pointer to load
It looks like lockless_dererence() has been used incorrectly
in the drm-intel tree commit since its argument must be a
pointer to be dererenced later. The same thing is done in
drivers/gpu/drm/i915/i915_gem.c as well.
I have applied the following hack patch for now, but this needs to be
fixed properly.
From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Tue, 5 Jul 2016 13:44:39 +1000
Subject: [PATCH] drm/i915: hack around bad use of lockless_dereference()
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
drivers/gpu/drm/i915/i915_gem.c | 2 +-
drivers/gpu/drm/i915/i915_irq.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d3502c0603e5..1f91f187b2a8 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3290,7 +3290,7 @@ i915_gem_retire_work_handler(struct work_struct *work)
* We do not need to do this test under locking as in the worst-case
* we queue the retire worker once too often.
*/
- if (lockless_dereference(dev_priv->gt.awake))
+ if (/*lockless_dereference*/(dev_priv->gt.awake))
queue_delayed_work(dev_priv->wq,
&dev_priv->gt.retire_work,
round_jiffies_up_relative(HZ));
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index f6de8dd567a2..2c1926418691 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -3095,7 +3095,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
if (!i915.enable_hangcheck)
return;
- if (!lockless_dereference(dev_priv->gt.awake))
+ if (!/*lockless_dereference*/(dev_priv->gt.awake))
return;
/* As enabling the GPU requires fairly extensive mmio access,
--
2.8.1
--
Cheers,
Stephen Rothwell
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: linux-next: build failure after merge of the tip tree (from the drm-intel tree)
2016-07-05 3:53 linux-next: build failure after merge of the tip tree (from the drm-intel tree) Stephen Rothwell
@ 2016-07-05 8:25 ` Peter Zijlstra
2016-07-05 17:59 ` Paul E. McKenney
0 siblings, 1 reply; 3+ messages in thread
From: Peter Zijlstra @ 2016-07-05 8:25 UTC (permalink / raw)
To: Stephen Rothwell
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, Daniel Vetter,
intel-gfx, dri-devel, linux-next, linux-kernel, Chris Wilson,
Paul McKenney
On Tue, Jul 05, 2016 at 01:53:03PM +1000, Stephen Rothwell wrote:
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index d3502c0603e5..1f91f187b2a8 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3290,7 +3290,7 @@ i915_gem_retire_work_handler(struct work_struct *work)
> * We do not need to do this test under locking as in the worst-case
> * we queue the retire worker once too often.
> */
> - if (lockless_dereference(dev_priv->gt.awake))
> + if (/*lockless_dereference*/(dev_priv->gt.awake))
> queue_delayed_work(dev_priv->wq,
> &dev_priv->gt.retire_work,
> round_jiffies_up_relative(HZ));
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index f6de8dd567a2..2c1926418691 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -3095,7 +3095,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
> if (!i915.enable_hangcheck)
> return;
>
> - if (!lockless_dereference(dev_priv->gt.awake))
> + if (!/*lockless_dereference*/(dev_priv->gt.awake))
> return;
>
> /* As enabling the GPU requires fairly extensive mmio access,
Right, neither case appears to include a data dependency and thus
lockless_dereference() seems misguided.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: linux-next: build failure after merge of the tip tree (from the drm-intel tree)
2016-07-05 8:25 ` Peter Zijlstra
@ 2016-07-05 17:59 ` Paul E. McKenney
0 siblings, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2016-07-05 17:59 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Stephen Rothwell, Thomas Gleixner, Ingo Molnar, H. Peter Anvin,
Daniel Vetter, intel-gfx, dri-devel, linux-next, linux-kernel,
Chris Wilson
On Tue, Jul 05, 2016 at 10:25:12AM +0200, Peter Zijlstra wrote:
> On Tue, Jul 05, 2016 at 01:53:03PM +1000, Stephen Rothwell wrote:
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index d3502c0603e5..1f91f187b2a8 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3290,7 +3290,7 @@ i915_gem_retire_work_handler(struct work_struct *work)
> > * We do not need to do this test under locking as in the worst-case
> > * we queue the retire worker once too often.
> > */
> > - if (lockless_dereference(dev_priv->gt.awake))
> > + if (/*lockless_dereference*/(dev_priv->gt.awake))
> > queue_delayed_work(dev_priv->wq,
> > &dev_priv->gt.retire_work,
> > round_jiffies_up_relative(HZ));
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index f6de8dd567a2..2c1926418691 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -3095,7 +3095,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
> > if (!i915.enable_hangcheck)
> > return;
> >
> > - if (!lockless_dereference(dev_priv->gt.awake))
> > + if (!/*lockless_dereference*/(dev_priv->gt.awake))
> > return;
> >
> > /* As enabling the GPU requires fairly extensive mmio access,
>
> Right, neither case appears to include a data dependency and thus
> lockless_dereference() seems misguided.
Agreed! At first glance, this code wants READ_ONCE() rather than
lockless_dereference().
Thanx, Paul
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-07-05 3:53 linux-next: build failure after merge of the tip tree (from the drm-intel tree) Stephen Rothwell
2016-07-05 8:25 ` Peter Zijlstra
2016-07-05 17:59 ` Paul E. McKenney
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