drm/xe: Stop accumulating LRC timestamp on job_free

The exec queue timestamp is only really useful when it's being queried
through the fdinfo. There's no need to update it so often, on every
job_free. Tracing a simple app like vkcube running shows an update
rate of ~ 120Hz. In case of discrete, the BO is on vram, creating a lot
of pcie transactions.

The update on job_free() is used to cover a gap: if exec
queue is created and destroyed rapidly, before a new query, the
timestamp still needs to be accumulated and accounted for in the xef.

Initial implementation in commit 6109f24 ("drm/xe: Add helper to
accumulate exec queue runtime") couldn't do it on the exec_queue_fini
since the xef could be gone at that point. However since commit
ce8c161 ("drm/xe: Add ref counting for xe_file") the xef is
refcounted and the exec queue always holds a reference, making this safe
now.

Improve the fix in commit 2149ded ("drm/xe: Fix use after free when
client stats are captured") by reducing the frequency in which the
update is needed.

Fixes: 2149ded ("drm/xe: Fix use after free when client stats are captured")
Reviewed-by: Nirmoy Das <[email protected]>
Reviewed-by: Jonathan Cavitt <[email protected]>
Reviewed-by: Umesh Nerlige Ramappa <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>
(cherry picked from commit 83db047)
Signed-off-by: Lucas De Marchi <[email protected]>

Author: lucasdemarchi

drivers/gpu/drm/xe/xe_exec_queue.c

@@ -260,8 +260,14 @@ void xe_exec_queue_fini(struct xe_exec_queue *q)
 {
 	int i;
 
+	/*
+	 * Before releasing our ref to lrc and xef, accumulate our run ticks
+	 */
+	xe_exec_queue_update_run_ticks(q);
+
 	for (i = 0; i < q->width; ++i)
 		xe_lrc_put(q->lrc[i]);
+
 	__xe_exec_queue_free(q);
 }
 

drivers/gpu/drm/xe/xe_guc_submit.c

@@ -745,8 +745,6 @@ static void guc_exec_queue_free_job(struct drm_sched_job *drm_job)
 {
 	struct xe_sched_job *job = to_xe_sched_job(drm_job);
 
-	xe_exec_queue_update_run_ticks(job->q);
-
 	trace_xe_sched_job_free(job);
 	xe_sched_job_put(job);
 }