Re: [PATCH 6.1.y 1/1] hrtimer: Use and report correct timerslack values for realtime tasks

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: ed4fb6d7ef68111bb539283561953e5c6e9a6e38

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Not found

Note: The patch differs from the upstream commit:
---
1:  ed4fb6d7ef681 ! 1:  a4d3916d07d4c hrtimer: Use and report correct timerslack values for realtime tasks
    @@ Metadata
      ## Commit message ##
         hrtimer: Use and report correct timerslack values for realtime tasks
     
    +    commit ed4fb6d7ef68111bb539283561953e5c6e9a6e38 upstream.
    +
         The timerslack_ns setting is used to specify how much the hardware
         timers should be delayed, to potentially dispatch multiple timers in a
         single interrupt. This is a performance optimization. Timers of
    @@ fs/select.c: u64 select_estimate_accuracy(struct timespec64 *tv)
      }
      
     
    - ## kernel/sched/syscalls.c ##
    -@@ kernel/sched/syscalls.c: static void __setscheduler_params(struct task_struct *p,
    + ## kernel/sched/core.c ##
    +@@ kernel/sched/core.c: static void __setscheduler_params(struct task_struct *p,
      	else if (fair_policy(policy))
      		p->static_prio = NICE_TO_PRIO(attr->sched_nice);
      
    @@ kernel/time/hrtimer.c: long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_m
     -	u64 slack;
     -
     -	slack = current->timer_slack_ns;
    --	if (rt_task(current))
    +-	if (dl_task(current) || rt_task(current))
     -		slack = 0;
      
      	hrtimer_init_sleeper_on_stack(&t, clockid, mode);
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |