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Message-ID: <20250716065707.GA32@bytedance>
Date: Wed, 16 Jul 2025 14:57:07 +0800
From: Aaron Lu <ziqianlu@...edance.com>
To: kernel test robot <lkp@...el.com>
Cc: 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 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.
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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