linux-kernel - Re: [PATCH 18/19] sched/fair: Avoid cache-aware scheduling for memory-heavy processes

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Message-ID: <a097ea5b-a4cf-4b47-91c2-6ba4b159a7e5@intel.com>
Date: Thu, 16 Oct 2025 12:44:10 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: kernel test robot <oliver.sang@...el.com>, Tim Chen
	<tim.c.chen@...ux.intel.com>
CC: <oe-lkp@...ts.linux.dev>, <lkp@...el.com>, <linux-kernel@...r.kernel.org>,
	<aubrey.li@...ux.intel.com>, Peter Zijlstra <peterz@...radead.org>, "Ingo
 Molnar" <mingo@...hat.com>, K Prateek Nayak <kprateek.nayak@....com>,
	"Gautham R . Shenoy" <gautham.shenoy@....com>, Vincent Guittot
	<vincent.guittot@...aro.org>, Juri Lelli <juri.lelli@...hat.com>, "Dietmar
 Eggemann" <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, "Valentin
 Schneider" <vschneid@...hat.com>, Madadi Vineeth Reddy
	<vineethr@...ux.ibm.com>, Hillf Danton <hdanton@...a.com>, Shrikanth Hegde
	<sshegde@...ux.ibm.com>, Jianyong Wu <jianyong.wu@...look.com>, Yangyu Chen
	<cyy@...self.name>, Tingyin Duan <tingyin.duan@...il.com>, Vern Hao
	<vernhao@...cent.com>, Len Brown <len.brown@...el.com>, Aubrey Li
	<aubrey.li@...el.com>, Zhao Liu <zhao1.liu@...el.com>, Chen Yu
	<yu.chen.surf@...il.com>, Libo Chen <libo.chen@...cle.com>, Adam Li
	<adamli@...amperecomputing.com>, Tim Chen <tim.c.chen@...el.com>
Subject: Re: [PATCH 18/19] sched/fair: Avoid cache-aware scheduling for
 memory-heavy processes

On 10/15/2025 2:57 PM, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed "UBSAN:array-index-out-of-bounds_in_drivers/base/cacheinfo.c" on:

[snip]

> [   12.549731][   T83] ------------[ cut here ]------------
> [   12.550388][   T83] UBSAN: array-index-out-of-bounds in drivers/base/cacheinfo.c:37:9
> [   12.551060][   T83] index 4294967295 is out of range for type 'unsigned long[8]'
> [   12.551580][   T83] CPU: 0 UID: 0 PID: 83 Comm: systemd-journal Not tainted 6.17.0-rc4-00035-ge8b871200f11 #1 PREEMPTLAZY
> [   12.551585][   T83] Call Trace:
> [   12.551588][   T83]  __dump_stack (lib/dump_stack.c:95)
> [   12.551594][   T83]  dump_stack_lvl (lib/dump_stack.c:123)
> [   12.551601][   T83]  ubsan_epilogue.llvm.16751680356772289369 (lib/dump_stack.c:129 lib/ubsan.c:233)
> [   12.551607][   T83]  __ubsan_handle_out_of_bounds (lib/ubsan.c:?)
> [   12.551621][   T83]  get_cpu_cacheinfo (drivers/base/cacheinfo.c:?)
> [   12.551625][   T83]  exceed_llc_capacity (include/linux/cacheinfo.h:? kernel/sched/fair.c:1256)

Thanks 0day! It seems that for some reason the assignment of curr_cpu = 
task_cpu(p);
was after the check exceed_llc_capacity(), will fix this.

thanks,
Chenyu