From: Will Deacon <will@kernel.org>
To: Song Shuai <songshuaishuai@tinylab.org>
Cc: catalin.marinas@arm.com, paul.walmsley@sifive.com,
palmer@dabbelt.com, aou@eecs.berkeley.edu, chris@zankel.net,
jcmvbkbc@gmail.com, steven.price@arm.com,
vincenzo.frascino@arm.com, pcc@google.com, wangxiang@cdjrlc.com,
ajones@ventanamicro.com, conor.dooley@microchip.com,
jeeheng.sia@starfivetech.com, leyfoon.tan@starfivetech.com,
linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
Subject: Re: [PATCH 2/4] arm64: hibernate: remove WARN_ON in save_processor_state
Date: Thu, 8 Jun 2023 18:26:58 +0100 [thread overview]
Message-ID: <20230608172656.GB1606@willie-the-truck> (raw)
In-Reply-To: <A8B3B45A0174F0B8+98d9d1e1-fe9f-9173-e5a7-b31113da861a@tinylab.org>
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
next prev parent reply other threads:[~2023-06-08 17:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-25 2:55 [PATCH 0/4] Remove WARN_ON in save_processor_state Song Shuai
2023-05-25 2:55 ` [PATCH 1/4] ARM: hibernate: remove " Song Shuai
2023-05-25 2:55 ` [PATCH 2/4] arm64: " Song Shuai
2023-06-05 14:28 ` Will Deacon
2023-06-07 3:00 ` Song Shuai
2023-06-08 17:26 ` Will Deacon [this message]
2023-05-25 2:55 ` [PATCH 3/4] riscv: " Song Shuai
2023-05-25 2:55 ` [PATCH 4/4] xtensa: " Song Shuai
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