netdev - Re: [Xen-devel] printk from softirq on xen: hard lockup

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Message-ID: <CAHmME9pNt3MxbiygL+XVYNJRQ6NGp1KqhpxcqtSzv5KOL1YSeQ@mail.gmail.com>
Date:	Wed, 5 Aug 2015 18:37:46 +0200
From:	"Jason A. Donenfeld" <Jason@...c4.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org,
	netdev@...r.kernel.org, Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	wei.liu2@...rix.com, Ian.Campbell@...rix.com,
	konrad.wilk@...cle.com
Subject: Re: [Xen-devel] printk from softirq on xen: hard lockup

Hi folks,

I have written an extremely simple reproducer. Xen 4.5.1. Linux 4.1.3.
Config attached. Reproducer attached. Makefile attached.

It results in the COMPLETE lockup of the system when it receives a
network packet over the Xen PV network interface.

The lockup is 100% reliable. As in the messages above, it puts this --
"while (native_apic_mem_read(APIC_ICR) & APIC_ICR_BUSY)" into a busy
loop that never exits.

It is triggered by a simple printk in softirq.

Thanks,
Jason

Download attachment "Makefile" of type "application/octet-stream" (194 bytes)

View attachment "xen-printk-crash.c" of type "text/x-csrc" (1006 bytes)

Download attachment "4.1.3-domU-config" of type "application/octet-stream" (55533 bytes)