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Message-ID: <aHdXam/+MRQp+MEf@rli9-mobl>
Date: Wed, 16 Jul 2025 15:40:26 +0800
From: Philip Li <philip.li@...el.com>
To: Aaron Lu <ziqianlu@...edance.com>
CC: kernel test robot <lkp@...el.com>, Valentin Schneider
<vschneid@...hat.com>, Ben Segall <bsegall@...gle.com>, K Prateek Nayak
<kprateek.nayak@....com>, Peter Zijlstra <peterz@...radead.org>, "Chengming
Zhou" <chengming.zhou@...ux.dev>, Josh Don <joshdon@...gle.com>, Ingo Molnar
<mingo@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Xi Wang
<xii@...gle.com>, <llvm@...ts.linux.dev>, <oe-kbuild-all@...ts.linux.dev>,
<linux-kernel@...r.kernel.org>, Juri Lelli <juri.lelli@...hat.com>, "Dietmar
Eggemann" <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>,
Mel Gorman <mgorman@...e.de>, Chuyi Zhou <zhouchuyi@...edance.com>, "Jan
Kiszka" <jan.kiszka@...mens.com>, Florian Bezdeka
<florian.bezdeka@...mens.com>, Songtang Liu <liusongtang@...edance.com>
Subject: Re: [PATCH v3 3/5] sched/fair: Switch to task based throttle model
On Wed, Jul 16, 2025 at 02:57:07PM +0800, Aaron Lu wrote:
> On Wed, Jul 16, 2025 at 07:29:37AM +0800, kernel test robot wrote:
> > Hi Aaron,
> >
> > kernel test robot noticed the following build warnings:
> >
> > [auto build test WARNING on tip/sched/core]
> > [also build test WARNING on next-20250715]
> > [cannot apply to linus/master v6.16-rc6]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Lu/sched-fair-Add-related-data-structure-for-task-based-throttle/20250715-152307
> > base: tip/sched/core
> > patch link: https://lore.kernel.org/r/20250715071658.267-4-ziqianlu%40bytedance.com
> > patch subject: [PATCH v3 3/5] sched/fair: Switch to task based throttle model
> > config: i386-buildonly-randconfig-006-20250716 (https://download.01.org/0day-ci/archive/20250716/202507160730.0cXkgs0S-lkp@intel.com/config)
> > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250716/202507160730.0cXkgs0S-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@...el.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202507160730.0cXkgs0S-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> > >> kernel/sched/fair.c:5456:33: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
> > 5456 | cfs_rq->pelt_clock_throttled = 1;
> > | ^ ~
>
> Thanks for the report.
>
> I don't think this will affect correctness since both cfs_rq's throttled
> and pelt_clock_throttled fields are used as true(not 0) or false(0). I
> used bitfield for them to save some space.
>
> Change their types to either unsigned int or bool should cure this
> warning, I suppose bool looks more clear?
>
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index dbe52e18b93a0..434f816a56701 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -737,8 +737,8 @@ struct cfs_rq {
> u64 throttled_clock_pelt_time;
> u64 throttled_clock_self;
> u64 throttled_clock_self_time;
> - int throttled:1;
> - int pelt_clock_throttled:1;
> + bool throttled:1;
> + bool pelt_clock_throttled:1;
> int throttle_count;
> struct list_head throttled_list;
> struct list_head throttled_csd_list;
>
> Hi LKP,
>
> I tried using clang-19 but couldn't reproduce this warning and I don't
> have clang-20 at hand. Can you please apply the above hunk on top of
> this series and see if that warning is gone? Thanks.
Got it, is it possible to give a try for the reproduce step [1], which can
download clang-20 to local dir? If it has issue, we will follow up to check
as early as possible.
[1] https://download.01.org/0day-ci/archive/20250716/202507160730.0cXkgs0S-lkp@intel.com/reproduce
>
> Best regards,
> Aaron
>
> > kernel/sched/fair.c:5971:32: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
> > 5971 | cfs_rq->pelt_clock_throttled = 1;
> > | ^ ~
> > kernel/sched/fair.c:6014:20: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
> > 6014 | cfs_rq->throttled = 1;
> > | ^ ~
> > 3 warnings generated.
> >
> >
> > vim +/int +5456 kernel/sched/fair.c
> >
> > 5372
> > 5373 static bool
> > 5374 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> > 5375 {
> > 5376 bool sleep = flags & DEQUEUE_SLEEP;
> > 5377 int action = UPDATE_TG;
> > 5378
> > 5379 update_curr(cfs_rq);
> > 5380 clear_buddies(cfs_rq, se);
> > 5381
> > 5382 if (flags & DEQUEUE_DELAYED) {
> > 5383 WARN_ON_ONCE(!se->sched_delayed);
> > 5384 } else {
> > 5385 bool delay = sleep;
> > 5386 /*
> > 5387 * DELAY_DEQUEUE relies on spurious wakeups, special task
> > 5388 * states must not suffer spurious wakeups, excempt them.
> > 5389 */
> > 5390 if (flags & DEQUEUE_SPECIAL)
> > 5391 delay = false;
> > 5392
> > 5393 WARN_ON_ONCE(delay && se->sched_delayed);
> > 5394
> > 5395 if (sched_feat(DELAY_DEQUEUE) && delay &&
> > 5396 !entity_eligible(cfs_rq, se)) {
> > 5397 update_load_avg(cfs_rq, se, 0);
> > 5398 set_delayed(se);
> > 5399 return false;
> > 5400 }
> > 5401 }
> > 5402
> > 5403 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)))
> > 5404 action |= DO_DETACH;
> > 5405
> > 5406 /*
> > 5407 * When dequeuing a sched_entity, we must:
> > 5408 * - Update loads to have both entity and cfs_rq synced with now.
> > 5409 * - For group_entity, update its runnable_weight to reflect the new
> > 5410 * h_nr_runnable of its group cfs_rq.
> > 5411 * - Subtract its previous weight from cfs_rq->load.weight.
> > 5412 * - For group entity, update its weight to reflect the new share
> > 5413 * of its group cfs_rq.
> > 5414 */
> > 5415 update_load_avg(cfs_rq, se, action);
> > 5416 se_update_runnable(se);
> > 5417
> > 5418 update_stats_dequeue_fair(cfs_rq, se, flags);
> > 5419
> > 5420 update_entity_lag(cfs_rq, se);
> > 5421 if (sched_feat(PLACE_REL_DEADLINE) && !sleep) {
> > 5422 se->deadline -= se->vruntime;
> > 5423 se->rel_deadline = 1;
> > 5424 }
> > 5425
> > 5426 if (se != cfs_rq->curr)
> > 5427 __dequeue_entity(cfs_rq, se);
> > 5428 se->on_rq = 0;
> > 5429 account_entity_dequeue(cfs_rq, se);
> > 5430
> > 5431 /* return excess runtime on last dequeue */
> > 5432 return_cfs_rq_runtime(cfs_rq);
> > 5433
> > 5434 update_cfs_group(se);
> > 5435
> > 5436 /*
> > 5437 * Now advance min_vruntime if @se was the entity holding it back,
> > 5438 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
> > 5439 * put back on, and if we advance min_vruntime, we'll be placed back
> > 5440 * further than we started -- i.e. we'll be penalized.
> > 5441 */
> > 5442 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
> > 5443 update_min_vruntime(cfs_rq);
> > 5444
> > 5445 if (flags & DEQUEUE_DELAYED)
> > 5446 finish_delayed_dequeue_entity(se);
> > 5447
> > 5448 if (cfs_rq->nr_queued == 0) {
> > 5449 update_idle_cfs_rq_clock_pelt(cfs_rq);
> > 5450 #ifdef CONFIG_CFS_BANDWIDTH
> > 5451 if (throttled_hierarchy(cfs_rq)) {
> > 5452 struct rq *rq = rq_of(cfs_rq);
> > 5453
> > 5454 list_del_leaf_cfs_rq(cfs_rq);
> > 5455 cfs_rq->throttled_clock_pelt = rq_clock_pelt(rq);
> > > 5456 cfs_rq->pelt_clock_throttled = 1;
> > 5457 }
> > 5458 #endif
> > 5459 }
> > 5460
> > 5461 return true;
> > 5462 }
> > 5463
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
>
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