(Forgot mail subject, add it)
On Sun, Apr 15, 2012 at 2:09 PM, Lin Ming <mlin@ss.pku.edu.cn>
wrote:> Hi all,
>
> These 2 patches try to fix the "perf top" soft lockups under Xen
> reported by Steven at: https://lkml.org/lkml/2012/2/9/506
>
> I tested it with 3.4-rc2 and "perf top" works well now.
>
> Steven,
> Could you please help to test it too?
>
> The soft lockup code path is:
>
> __irq_work_queue
> arch_irq_work_raise
> apic->send_IPI_self(IRQ_WORK_VECTOR);
> apic_send_IPI_self
> __default_send_IPI_shortcut
> __xapic_wait_icr_idle
>
> static inline void __xapic_wait_icr_idle(void)
> {
> while (native_apic_mem_read(APIC_ICR) & APIC_ICR_BUSY)
> cpu_relax();
> }
>
> The lockup happens at above while looop.
>
> The cause is that Xen has not implemented the APIC IPI interface yet.
> Xen has IPI interface: xen_send_IPI_one, but it''s only used in
> xen_smp_send_reschedule, xen_smp_send_call_function_ipi and
> xen_smp_send_call_function_single_ipi, etc.
>
> So we need to implement Xen''s APIC IPI interface as Ben''s
patch does.
> And implement Xen''s IRQ_WORK_VECTOR handler.
>
> Ben Guthro (1):
> xen: implement apic ipi interface
>
> Lin Ming (1):
> xen: implement IRQ_WORK_VECTOR handler
>
> arch/x86/include/asm/xen/events.h | 1 +
> arch/x86/xen/enlighten.c | 7 ++
> arch/x86/xen/smp.c | 111
+++++++++++++++++++++++++++++++++++-
> arch/x86/xen/smp.h | 12 ++++
> 4 files changed, 127 insertions(+), 4 deletions(-)
>
> Any comment is appreciated.
> Lin Ming
