linux-kernel - Re: [PATCH v4] cpuidle: Init cpuidle only for present CPUs

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Message-ID: <Z8rBYuDiIyo8y6HT@bogus>
Date: Fri, 7 Mar 2025 09:50:26 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Jacky Bai <ping.bai@....com>
Cc: <rafael@...nel.org>, <daniel.lezcano@...aro.org>,
	<lpieralisi@...nel.org>, <ulf.hansson@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>, <james.morse@....com>,
	<d-gole@...com>, <anup@...infault.org>, <paul.walmsley@...ive.com>,
	<palmer@...belt.com>, <aou@...s.berkeley.edu>,
	<linux-pm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
	<imx@...ts.linux.dev>, <khilman@...libre.com>,
	<quic_tingweiz@...cinc.com>, <quic_yuanjiey@...cinc.com>
Subject: Re: [PATCH v4] cpuidle: Init cpuidle only for present CPUs

On Fri, Mar 07, 2025 at 04:03:03PM +0800, Jacky Bai wrote:
> for_each_possible_cpu() is currently used to initialize cpuidle
> in below cpuidle drivers:
>   drivers/cpuidle/cpuidle-arm.c
>   drivers/cpuidle/cpuidle-big_little.c
>   drivers/cpuidle/cpuidle-psci.c
>   drivers/cpuidle/cpuidle-riscv-sbi.c
> 
> However, in cpu_dev_register_generic(), for_each_present_cpu()
> is used to register CPU devices which means the CPU devices are
> only registered for present CPUs and not all possible CPUs.
> 
> With nosmp or maxcpus=0, only the boot CPU is present, lead
> to the failure:
> 
>   |  Failed to register cpuidle device for cpu1
> 
> Then rollback to cancel all CPUs' cpuidle registration.
> 
> Change for_each_possible_cpu() to for_each_present_cpu() in the
> above cpuidle drivers to ensure it only registers cpuidle devices
> for CPUs that are actually present.
> 
> Fixes: b0c69e1214bc ("drivers: base: Use present CPUs in GENERIC_CPU_DEVICES")
> Reviewed-by: Dhruva Gole <d-gole@...com>
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> Tested-by: Yuanjie Yang <quic_yuanjiey@...cinc.com>
> Signed-off-by: Jacky Bai <ping.bai@....com>
> ---
>  - v4 changes:
>   - add changes for other cpuidle driver that has the similar issue
>     as cpuidle-pcsi driver.
> 
>  - v3 changes:
>   - improve the changelog as suggested by Sudeep
> ---
>  drivers/cpuidle/cpuidle-arm.c        | 8 ++++----
>  drivers/cpuidle/cpuidle-big_little.c | 2 +-
>  drivers/cpuidle/cpuidle-psci.c       | 4 ++--
>  drivers/cpuidle/cpuidle-riscv-sbi.c  | 4 ++--


Why have you spared drivers/cpuidle/cpuidle-qcom-spm.c ? IIUC the issue
exists there as well.

-- 
Regards,
Sudeep