linux-kernel - Re: [tip:sched/core] [sched/smp] 06ddd17521: BUG:using_smp_processor_id()in

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Message-ID: <99573578-95e8-4b97-b2c8-d8229e4816e5@intel.com>
Date: Thu, 10 Jul 2025 16:29:51 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
CC: kernel test robot <oliver.sang@...el.com>, Ingo Molnar <mingo@...nel.org>,
	<oe-lkp@...ts.linux.dev>, <lkp@...el.com>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Dietmar Eggemann
	<dietmar.eggemann@....com>, Juri Lelli <juri.lelli@...hat.com>, "Linus
 Torvalds" <torvalds@...ux-foundation.org>, Mel Gorman <mgorman@...e.de>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>, Steven Rostedt
	<rostedt@...dmis.org>, Valentin Schneider <vschneid@...hat.com>, "Vincent
 Guittot" <vincent.guittot@...aro.org>, <aubrey.li@...ux.intel.com>
Subject: Re: [tip:sched/core] [sched/smp] 06ddd17521:
 BUG:using_smp_processor_id()in_preemptible

On 7/10/2025 4:11 PM, Sebastian Andrzej Siewior wrote:
> On 2025-07-10 16:00:46 [+0800], Chen, Yu C wrote:
>> migrate_disable() disables the task migration between CPUs by restricting
>> the task's affinity, but it does not disable the preemption on single
>> CPUs IMO. The scope of guard(preempt)() in migrate_disable() is just
>> within the migrate_disable(). debug_smp_processor_id() warns when the
>> preemption is enabled.
> 
> does migrate_disable() really have no effect on
> debug_smp_processor_id()?
> 

I see. So there is still a CONFIG_SMP to check migrate_disbled
in debug_smp_processor_id(), and that was skipped if we do not
have CONFIG_SMP set.


thanks,
Chenyu>> Thanks,
>> Chenyu
> Sebastian