[RFC PATCH 2/2] drm/i915: Adjust to RCU-less fence

[Philipp Stanner]

dma_fence has been reworked in a way that it allows for handling fences
without any need for RCU functionality.

Adjust i915 accordingly.

(Serves as an example to show how the situation gets easier for users)

Signed-off-by: Philipp Stanner <phasta@xxxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/intel_gt_requests.c | 10 ++++------
 drivers/gpu/drm/i915/i915_request.c         |  6 ++----
 drivers/gpu/drm/i915/i915_sw_fence.c        | 10 ++++------
 3 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
index 93298820bee2..724c4359f688 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
@@ -238,6 +238,8 @@ void intel_gt_fini_requests(struct intel_gt *gt)
 
 void intel_gt_watchdog_work(struct work_struct *work)
 {
+	char driver[64] = "";
+	char timeline[64] = "";
 	struct intel_gt *gt =
 		container_of(work, typeof(*gt), watchdog.work);
 	struct i915_request *rq, *rn;
@@ -250,17 +252,13 @@ void intel_gt_watchdog_work(struct work_struct *work)
 	llist_for_each_entry_safe(rq, rn, first, watchdog.link) {
 		if (!i915_request_completed(rq)) {
 			struct dma_fence *f = &rq->fence;
-			const char __rcu *timeline;
-			const char __rcu *driver;
 
-			rcu_read_lock();
-			driver = dma_fence_driver_name(f);
-			timeline = dma_fence_timeline_name(f);
+			dma_fence_driver_name(f, driver, 64);
+			dma_fence_timeline_name(f, timeline, 64);
 			pr_notice("Fence expiration time out i915-%s:%s:%llx!\n",
 				  rcu_dereference(driver),
 				  rcu_dereference(timeline),
 				  f->seqno);
-			rcu_read_unlock();
 			i915_request_cancel(rq, -EINTR);
 		}
 		i915_request_put(rq);
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index d2c7b1090df0..2a3df13217b9 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -2185,7 +2185,7 @@ void i915_request_show(struct drm_printer *m,
 		       const char *prefix,
 		       int indent)
 {
-	const char __rcu *timeline;
+	char timeline[64] = "";
 	char buf[80] = "";
 	int x = 0;
 
@@ -2221,8 +2221,7 @@ void i915_request_show(struct drm_printer *m,
 
 	x = print_sched_attr(&rq->sched.attr, buf, x, sizeof(buf));
 
-	rcu_read_lock();
-	timeline = dma_fence_timeline_name((struct dma_fence *)&rq->fence);
+	dma_fence_timeline_name((struct dma_fence *)&rq->fence, timeline, 64);
 	drm_printf(m, "%s%.*s%c %llx:%lld%s%s %s @ %dms: %s\n",
 		   prefix, indent, "                ",
 		   queue_status(rq),
@@ -2232,7 +2231,6 @@ void i915_request_show(struct drm_printer *m,
 		   buf,
 		   jiffies_to_msecs(jiffies - rq->emitted_jiffies),
 		   rcu_dereference(timeline));
-	rcu_read_unlock();
 }
 
 static bool engine_match_ring(struct intel_engine_cs *engine, struct i915_request *rq)
diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
index f24f616e23ee..d0e733beff86 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.c
+++ b/drivers/gpu/drm/i915/i915_sw_fence.c
@@ -427,25 +427,23 @@ static void dma_i915_sw_fence_wake(struct dma_fence *dma,
 
 static void timer_i915_sw_fence_wake(struct timer_list *t)
 {
+	char driver[64] = "";
+	char timeline[64] = "";
 	struct i915_sw_dma_fence_cb_timer *cb = timer_container_of(cb, t,
 								   timer);
 	struct i915_sw_fence *fence;
-	const char __rcu *timeline;
-	const char __rcu *driver;
 
 	fence = xchg(&cb->base.fence, NULL);
 	if (!fence)
 		return;
 
-	rcu_read_lock();
-	driver = dma_fence_driver_name(cb->dma);
-	timeline = dma_fence_timeline_name(cb->dma);
+	dma_fence_driver_name(cb->dma, driver, 64);
+	dma_fence_timeline_name(cb->dma, timeline, 64);
 	pr_notice("Asynchronous wait on fence %s:%s:%llx timed out (hint:%ps)\n",
 		  rcu_dereference(driver),
 		  rcu_dereference(timeline),
 		  cb->dma->seqno,
 		  i915_sw_fence_debug_hint(fence));
-	rcu_read_unlock();
 
 	i915_sw_fence_set_error_once(fence, -ETIMEDOUT);
 	i915_sw_fence_complete(fence);
-- 
2.55.0