[PATCH 3/4] drm/i915: non-interruptible sleeps can't handle -EGAIN

Daniel Vetter
2012-06-26T21:09:11Z

So don't return -EAGAIN, even in the case of a gpu hang. Remap it to -EIO
instead.

This is a bit ugly because intel_ring_begin is all non-interruptible
and hence only returns -EIO. But as the comment in there says,
auditing all the callsites would be a pain.

To avoid duplicating code, reuse i915_gem_check_wedge in __wait_seqno
and intel_wait_ring_buffer. Also use the opportunity to clarify the
different cases in i915_gem_check_wedge a bit with comments.

v2: Don't access dev_priv->mm.interruptible from check_wedge - we
might not hold dev->struct_mutex, making this racy. Instead pass
interruptible in as a parameter. I've noticed this because I've hit a
BUG_ON(!mutex_is_locked) at the top of check_wedge. This has been
added in

commit b4aca0106c466b5a0329318203f65bac2d91b682
Author: Ben Widawsky <ben@bwidawsk.net>
Date: Wed Apr 25 20:50:12 2012 -0700

drm/i915: extract some common olr+wedge code

although that commit is missing any justification for this it. I guess
it's just copy&paste, because the same commit add the same BUG_ON
check to check_olr, where it indeed makes sense.

But in check_wedge everything we access is protected by other means,
so this is superflous. And because it now gets in the way (we add a
new caller in __wait_seqno, which can be called without
dev->struct_mutext) let's just remove it.

v3: Group all the i915_gem_check_wedge refactoring into this patch, so
that this patch here is all about not returning -EAGAIN to callsites
that can't handle syscall restarting.

Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/i915/i915_drv.h | 2 ++
drivers/gpu/drm/i915/i915_gem.c | 26 ++++++++++++++++++--------
drivers/gpu/drm/i915/intel_ringbuffer.c | 6 ++++--
3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a0c15ab..ab9ade0 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1330,6 +1330,8 @@ i915_gem_object_unpin_fence(struct drm_i915_gem_object *obj)

void i915_gem_retire_requests(struct drm_device *dev);
void i915_gem_retire_requests_ring(struct intel_ring_buffer *ring);
+int __must_check i915_gem_check_wedge(struct drm_i915_private *dev_priv,
+ bool interruptible);

void i915_gem_reset(struct drm_device *dev);
void i915_gem_clflush_object(struct drm_i915_gem_object *obj);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6a98c06..af6a510 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1863,11 +1863,10 @@ i915_gem_retire_work_handler(struct work_struct *work)
mutex_unlock(&dev->struct_mutex);
}

-static int
-i915_gem_check_wedge(struct drm_i915_private *dev_priv)
+int
+i915_gem_check_wedge(struct drm_i915_private *dev_priv,
+ bool interruptible)
{
- BUG_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
-
if (atomic_read(&dev_priv->mm.wedged)) {
struct completion *x = &dev_priv->error_completion;
bool recovery_complete;
@@ -1878,7 +1877,16 @@ i915_gem_check_wedge(struct drm_i915_private *dev_priv)
recovery_complete = x->done > 0;
spin_unlock_irqrestore(&x->wait.lock, flags);

- return recovery_complete ? -EIO : -EAGAIN;
+ /* Non-interruptible callers can't handle -EAGAIN, hence return
+ * -EIO unconditionally for these. */
+ if (!interruptible)
+ return -EIO;
+
+ /* Recovery complete, but still wedged means reset failure. */
+ if (recovery_complete)
+ return -EIO;
+
+ return -EAGAIN;
}

return 0;
@@ -1932,6 +1940,7 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
unsigned long timeout_jiffies;
long end;
bool wait_forever = true;
+ int ret;

if (i915_seqno_passed(ring->get_seqno(ring), seqno))
return 0;
@@ -1963,8 +1972,9 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
end = wait_event_timeout(ring->irq_queue, EXIT_COND,
timeout_jiffies);

- if (atomic_read(&dev_priv->mm.wedged))
- end = -EAGAIN;
+ ret = i915_gem_check_wedge(dev_priv, interruptible);
+ if (ret)
+ end = ret;
} while (end == 0 && wait_forever);

getrawmonotonic(&now);
@@ -2004,7 +2014,7 @@ i915_wait_seqno(struct intel_ring_buffer *ring, uint32_t seqno)

BUG_ON(seqno == 0);

- ret = i915_gem_check_wedge(dev_priv);
+ ret = i915_gem_check_wedge(dev_priv, dev_priv->mm.interruptible);
if (ret)
return ret;

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 501546e..6c024d4 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1220,8 +1220,10 @@ int intel_wait_ring_buffer(struct intel_ring_buffer *ring, int n)
}

msleep(1);
- if (atomic_read(&dev_priv->mm.wedged))
- return -EAGAIN;
+
+ ret = i915_gem_check_wedge(dev_priv, dev_priv->mm.interruptible);
+ if (ret)
+ return ret;
} while (!time_after(jiffies, end));
trace_i915_ring_wait_end(ring);
return -EBUSY;
--
1.7.10