linux-kernel - Re: [PATCH V2 2/4] arm64: hibernate: remove WARN_ON in save_processor

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Message-ID: <20230609102315.GA3847@willie-the-truck>
Date:   Fri, 9 Jun 2023 11:23:16 +0100
From:   Will Deacon <will@...nel.org>
To:     Song Shuai <songshuaishuai@...ylab.org>
Cc:     catalin.marinas@....com, paul.walmsley@...ive.com,
        palmer@...belt.com, aou@...s.berkeley.edu, chris@...kel.net,
        jcmvbkbc@...il.com, steven.price@....com,
        vincenzo.frascino@....com, leyfoon.tan@...rfivetech.com,
        mason.huo@...rfivetech.com, jeeheng.sia@...rfivetech.com,
        conor.dooley@...rochip.com, ajones@...tanamicro.com,
        linux@...linux.org.uk, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH V2 2/4] arm64: hibernate: remove WARN_ON in
 save_processor_state

On Fri, Jun 09, 2023 at 03:50:47PM +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.
> 
> In the case of CONFIG_PM_SLEEP_SMP=n, freeze_secondary_cpus
> is not defined, but 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.
> 
> So remove the unnecessary checking in save_processor_state.
> 
> Signed-off-by: Song Shuai <songshuaishuai@...ylab.org>
> ---
>  arch/arm64/kernel/hibernate.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
> index 788597a6b6a2..02870beb271e 100644
> --- a/arch/arm64/kernel/hibernate.c
> +++ b/arch/arm64/kernel/hibernate.c
> @@ -99,7 +99,6 @@ int pfn_is_nosave(unsigned long pfn)
>  
>  void notrace save_processor_state(void)
>  {
> -	WARN_ON(num_online_cpus() != 1);
>  }
>  
>  void notrace restore_processor_state(void)

Acked-by: Will Deacon <will@...nel.org>

Thanks!

Will