From: Thomas Gleixner <tglx@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>,
Sneh Mankad <sneh.mankad@oss.qualcomm.com>
Cc: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Pavel Machek <pavel@kernel.org>, Len Brown <lenb@kernel.org>,
linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org
Subject: Re: [PATCH] kernel/cpu: Disallow offlining boot CPU based on config
Date: Fri, 05 Jun 2026 14:20:57 +0200 [thread overview]
Message-ID: <87ik7x5gba.ffs@fw13> (raw)
In-Reply-To: <20260605104330.GX3102624@noisy.programming.kicks-ass.net>
On Fri, Jun 05 2026 at 12:43, Peter Zijlstra wrote:
> On Fri, Jun 05, 2026 at 04:00:46PM +0530, Sneh Mankad wrote:
>> The Qualcomm SoCs like LeMans, Monaco support suspend to ram which leads
>> the SoC to ACPI S3 similar state where SoC is turned off and DDR is
>> retained.
>> The hardware design on these SoCs forces a constraint to suspend and
>> resume the system on boot CPU / CPU0.
>>
>> If CPU0 is already offline before starting suspend to ram the
>> freeze_secondary_cpus() picks alternate CPU as primary / last CPU and
>> proceed further to invoke PSCI SYSTEM_SUSPEND.
>> This leads to a system crash.
>>
>> In order to prevent such an issue introduce PM_SLEEP_SMP_CPU_ZERO_STRICT
>> config and when enabled prohibit the CPU0 to be offline.
>
> Why do this in generic code? Why can't this live in arch code.
> Specifically, x86 can't typically unplug CPU0 at all either.
arch_cpu_is_hotpluggable(cpu) provides that info to the cpu device core.
No hackery in cpu.c required at all.
Thanks,
tglx
next prev parent reply other threads:[~2026-06-05 12:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-05 10:30 [PATCH] kernel/cpu: Disallow offlining boot CPU based on config Sneh Mankad
2026-06-05 10:43 ` Peter Zijlstra
2026-06-05 12:20 ` Thomas Gleixner [this message]
2026-06-05 13:07 ` Pankaj Patil
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