Re: [PATCH] sched/stats: Fix run_delay over-count for proxy-migrated blocked donors

[K Prateek Nayak <kprateek.nayak@amd.com>]

On 10/27/2026 12:22 PM, Kayra Cizmeci wrote:
> I think this fixes the issue. BTW I think this should skip curr, no?
> On a case like this:
> 
> C holds M1 in CPU0, D waits that mutex in CPU1. A holds mutex M2 in
> CPU2. B is the working task on CPU1 but it wants mutex M2 and we enter
> __schedule(). B gets is_blocked. D gets chosen. We open the rq lock to
> get D to CPU0. While this happens A drops the mutex and wakes up B.
> we enter ttwu_runnable() and B is still curr. And we start the timer.

Good catch that!

> Or am I MISSSING something?

I can't believe something like wait time accounting can get this
complicated! Anyhow, We can perhaps call sched_info_enqueue() in
ttwu_runnable() instead of proxy_needs_return() like:

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 04b62c16fa8c..d5758b78b741 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3956,6 +3956,8 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags)
 		 * it should preempt the task that is current now.
 		 */
 		wakeup_preempt(rq, p, wake_flags | WF_TTWU_RQ);
+		/* Start accounting wait time. */
+		sched_info_enqueue(rq, p);
 	}
 	ttwu_do_wakeup(p);
 	return 1;
---

-- 
Thanks and Regards,
Prateek