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

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?

David