[Intel-gfx] [PATCH] drm/i915: Don't mix srcu tag and negative error codes

[Chris Wilson]

While srcu may use an integer tag, it does not exclude potential error
codes and so may overlap with our own use of -EINTR. Use a separate
outparam to store the tag, and report the error code separately. While
changing the function signature allow the caller to choose whether or not
the potential wait may be interrupted.

Fixes: 2caffbf11762 ("drm/i915: Revoke mmaps and prevent access to fence registers across reset")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c |  6 ++----
 drivers/gpu/drm/i915/gt/intel_reset.c    | 15 +++++++--------
 drivers/gpu/drm/i915/gt/intel_reset.h    |  2 +-
 3 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 82db2b783123..5701f213d63f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -245,11 +245,9 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 
 	wakeref = intel_runtime_pm_get(rpm);
 
-	srcu = intel_gt_reset_trylock(ggtt->vm.gt);
-	if (srcu < 0) {
-		ret = srcu;
+	ret = intel_gt_reset_lock(ggtt->vm.gt, TASK_INTERRUPTIBLE, &srcu);
+	if (ret)
 		goto err_rpm;
-	}
 
 	ret = i915_mutex_lock_interruptible(dev);
 	if (ret)
diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index 296bbc7745fb..9a10b857cc93 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -1214,10 +1214,8 @@ void intel_gt_handle_error(struct intel_gt *gt,
 	intel_runtime_pm_put(&gt->i915->runtime_pm, wakeref);
 }
 
-int intel_gt_reset_trylock(struct intel_gt *gt)
+int intel_gt_reset_lock(struct intel_gt *gt, int state, int *srcu)
 {
-	int srcu;
-
 	might_lock(&gt->reset.backoff_srcu);
 	might_sleep();
 
@@ -1225,17 +1223,18 @@ int intel_gt_reset_trylock(struct intel_gt *gt)
 	while (test_bit(I915_RESET_BACKOFF, &gt->reset.flags)) {
 		rcu_read_unlock();
 
-		if (wait_event_interruptible(gt->reset.queue,
-					     !test_bit(I915_RESET_BACKOFF,
-						       &gt->reset.flags)))
+		if (___wait_event(gt->reset.queue,
+				  !test_bit(I915_RESET_BACKOFF,
+					    &gt->reset.flags),
+				  state, 0, 0, schedule()))
 			return -EINTR;
 
 		rcu_read_lock();
 	}
-	srcu = srcu_read_lock(&gt->reset.backoff_srcu);
+	*srcu = srcu_read_lock(&gt->reset.backoff_srcu);
 	rcu_read_unlock();
 
-	return srcu;
+	return 0;
 }
 
 void intel_gt_reset_unlock(struct intel_gt *gt, int tag)
diff --git a/drivers/gpu/drm/i915/gt/intel_reset.h b/drivers/gpu/drm/i915/gt/intel_reset.h
index 37a987b17108..72cb172e1982 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.h
+++ b/drivers/gpu/drm/i915/gt/intel_reset.h
@@ -38,7 +38,7 @@ int intel_engine_reset(struct intel_engine_cs *engine,
 
 void __i915_request_reset(struct i915_request *rq, bool guilty);
 
-int __must_check intel_gt_reset_trylock(struct intel_gt *gt);
+int intel_gt_reset_lock(struct intel_gt *gt, int state, int *srcu);
 void intel_gt_reset_unlock(struct intel_gt *gt, int tag);
 
 void intel_gt_set_wedged(struct intel_gt *gt);
-- 
2.23.0