[RFC 20/39] drm/i915: Added scheduler support to page fault handler

John.C.Harrison
2015-07-17T14:34:13Z

GPU page faults can now require scheduler operation in order to complete. For
example, in order to free up sufficient memory to handle the fault the handler
must wait for a batch buffer to complete that has not even been sent to the
hardware yet. Thus EAGAIN no longer means a GPU hang, it can occur under normal
operation.

Change-Id: Iff6bd2744ef12bb7405fbcd6b43c286caad4141f
For: VIZ-1587
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
---
drivers/gpu/drm/i915/i915_gem.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index f713cda..dd9ebbe 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1919,10 +1919,15 @@ out:
}
case -EAGAIN:
/*
- * EAGAIN means the gpu is hung and we'll wait for the error
- * handler to reset everything when re-faulting in
+ * EAGAIN can mean the gpu is hung and we'll have to wait for
+ * the error handler to reset everything when re-faulting in
* i915_mutex_lock_interruptible.
+ *
+ * It can also indicate various other nonfatal errors for which
+ * the best response is to give other threads a chance to run,
+ * and then retry the failing operation in its entirety.
*/
+ /*FALLTHRU*/
case 0: