Re: [PATCH 2/4] arm64: hibernate: remove WARN_ON in save_processor_state

[Will Deacon]

On Wed, Jun 07, 2023 at 11:00:08AM +0800, Song Shuai wrote:
> 
> 
> 在 2023/6/5 22:28, Will Deacon 写道:
> > On Thu, May 25, 2023 at 10:55:53AM +0800, Song Shuai wrote:
> > > During hibernation or restoration, freeze_secondary_cpus
> > > checks num_online_cpus via BUG_ON, and the subsequent
> > > save_processor_state also does the checking with WARN_ON.
> > > 
> > > So remove the unnecessary checking in save_processor_state.
> > 
> > This is a very terse summary of why this is safe.
> > 
> > Looking at the code, freeze_secondary_cpus() does indeed check
> > num_online_cpus(), or it returns an error which then causes the hibernation
> > to fail. However, this is all in the CONFIG_PM_SLEEP_SMP=y case and it's
> > far less clear whether your assertion is true if that option is disabled.
> > 
> > Please can you describe your reasoning in more detail, and cover the case
> > where CONFIG_PM_SLEEP_SMP=n as well, please?
> 
> With HIBERNATION enabled, the sole possible condition to disable
> CONFIG_PM_SLEEP_SMP
> is !SMP where num_online_cpus is always 1. We also don't have to check it in
> save_processor_state.

Thanks. Please add that to the commit message.

Will