linux-kernel - RE: [PATCH v4 0/7] x86: BSP or CPU0 online/offline

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Message-ID: <43F901BD926A4E43B106BF17856F075501A22B5A21@orsmsx508.amr.corp.intel.com>
Date:	Tue, 6 Dec 2011 16:04:56 -0800
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Ingo Molnar <mingo@...e.hu>, Borislav Petkov <bp@...64.org>
CC:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Thomas Gleixner <tglx@...utronix.de>,
	H Peter Anvin <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Brown, Len" <len.brown@...el.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...r.kernel.org>, x86 <x86@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	"Herrmann3, Andreas" <Andreas.Herrmann3@....com>
Subject: RE: [PATCH v4 0/7] x86: BSP or CPU0 online/offline

> 
> The specific point i tried to make about s2ram is to make sure
> it does not break during normal usage: for example someone
> offlines the boot CPU, but the box then gets suspended - that
> should not hang or crash.
> 
This has been considered in the patch #7/7. There shouldn't be a problem here (in theory).

Suspend/hibernate calls callback bsp_pm_callback() and must pass this check before it can continue.

When CPU0 is offline, bsp_pm_callback() returns -ENODEV and suspend/hibernate fails. When CPU0 is online, bsp_pm_callback() returns 0 and suspend/hibernate can continue.

So when CPU0 is offline, system cannot suspend/hibernate. Suspend/hibernate can succeed only when CPU0 is online.

Plus the patch #7/7 considers race condition by pm_notifier_call_chain()'s priority in pm call chain. So there should be race issue here.

Thanks.

-Fenghua
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