linux-kernel - Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]

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Message-ID: <20071210091052.GA14487@elte.hu>
Date:	Mon, 10 Dec 2007 10:10:52 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	ego@...ibm.com, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Dipankar Sarma <dipankar@...ibm.com>
Subject: Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]


> > softlockup: remove get_online_cpus() which doesn't help here.
> > 
> > The get_online_cpus() protection seems to be bogus in 
> > kernel/softlockup.c as cpu cached in check_cpu can go offline once 
> > we do a put_online_cpus().
> > 
> > This can also cause deadlock during a cpu offline as follows:

i'm wondering, what's the proper CPU-hotplug safe sequence here then? 
I'm picking a CPU number from cpu_online_map, and that CPU could go away 
while i'm still using it, right? What's saving us here?

	Ingo
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