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From: Andi Kleen <andi@firstfloor.org>
To: Igor Mammedov <imammedo@redhat.com>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
	mingo@redhat.com, hpa@zytor.com, x86@kernel.org, bp@suse.de,
	paul.gortmaker@windriver.com, JBeulich@suse.com,
	prarit@redhat.com, drjones@redhat.com, toshi.kani@hp.com,
	riel@redhat.com, gong.chen@linux.intel.com
Subject: Re: [PATCH v2 1/5] x86: replace timeouts when booting secondary CPU with infinite wait loop
Date: Wed, 02 Apr 2014 10:15:29 -0700	[thread overview]
Message-ID: <87ppkzk5zi.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <1396296565-19709-2-git-send-email-imammedo@redhat.com> (Igor Mammedov's message of "Mon, 31 Mar 2014 22:09:21 +0200")

Igor Mammedov <imammedo@redhat.com> writes:

> Hang is observed on virtual machines during CPU hotplug,
> especially in big guests with many CPUs. (It reproducible
> more often if host is over-committed).
>
> It happens because master CPU gives up waiting on
> secondary CPU and allows it to run wild. As result
> AP causes locking or crashing system. For example
> as described here: https://lkml.org/lkml/2014/3/6/257
>
> If master CPU have sent STARTUP IPI successfully,
> make it wait indefinitely till AP boots.


But what happens on a real machine when the other CPU is dead?

I've seen that. Kernel still boots. With your patch it would
hang.

I don't think you can do that. It needs to have some timeout.
Maybe a longer or configurable one?

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only

  reply	other threads:[~2014-04-02 17:58 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-31 20:09 [PATCH v2 0/5] x86: fix hang when AP bringup is too slow Igor Mammedov
2014-03-31 20:09 ` [PATCH v2 1/5] x86: replace timeouts when booting secondary CPU with infinite wait loop Igor Mammedov
2014-04-02 17:15   ` Andi Kleen [this message]
2014-04-02 21:29     ` Igor Mammedov
2014-04-02 23:48       ` Andi Kleen
2014-04-03  6:43       ` Ingo Molnar
2014-04-03 21:03         ` Andi Kleen
2014-03-31 20:09 ` [PATCH v2 2/5] x86: cleanup not needed cpu_initialized_mask Igor Mammedov
2014-03-31 20:09 ` [PATCH v2 3/5] x86: log error on secondary CPU wakeup failure at ERR level Igor Mammedov
2014-03-31 20:09 ` [PATCH v2 4/5] x86: fix list corruption on CPU hotplug Igor Mammedov
2014-03-31 20:09 ` [PATCH v2 5/5] x86: fix memory corruption in acpi_unmap_lsapic() Igor Mammedov

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