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

[Sudeep Holla]

On Fri, Mar 07, 2025 at 10:02:14AM +0000, Jacky Bai wrote:
> Hi Sudeep,
> 
> > 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@xxxxxx>
> > > Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> > > Tested-by: Yuanjie Yang <quic_yuanjiey@xxxxxxxxxxx>
> > > Signed-off-by: Jacky Bai <ping.bai@xxxxxxx>
> > > ---
> > >  - 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.
> > 
> 
> For qcom-spm driver, it has below code logic to handle no cpu device case, and
> no rollback to cancel the whole cpuidle registration. So I just leave it as it is.
> Do we need to update it?
> 
> for_each_possible_cpu(cpu) {
>         ret = spm_cpuidle_register(&pdev->dev, cpu);

Did you look into this function ?

-- 
Regards,
Sudeep