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

From: David Vrabel
Date: Tue Aug 04 2015 - 13:14:33 EST

On 04/08/15 17:41, Jason A. Donenfeld wrote:
> Hi folks,
> Paul McKenney and I had an offline discussion about some rcu questions
> that eventually lead into me investigating a strange full lock-up I'm
> experiencing as a consequence of a printk in softirq inside of an
> rcu_read_lock, when using Xen PV. Relevant excerpts of the
^^ PV guest?

> (gdb) target remote localhost:9999
> Remote debugging using localhost:9999
> __xapic_wait_icr_idle () at ./arch/x86/include/asm/ipi.h:56
> 56 while (native_apic_mem_read(APIC_ICR) & APIC_ICR_BUSY)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ => HVM guest

Which is it?

A HVM guest's serial console may be particularly slow (since it's
emulated by qemu). Try using the PV console?

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