On Tue, 2015-08-04 at 18:12 +0100, David Vrabel wrote: > 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?
Aren't there still some code paths for PV guests which hit the native APIC case (emulated in Xen even for PV these days, since pvops in the early days didn't accept the hooks needed to make use of the hypercall versions of apic read/write). In particular I'm thinking of the IPI which is (or was) used by the sysrq to trigger the backtrace on all CPUs. Ian. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
