Messages in this thread | | | Date | Thu, 19 Feb 2015 08:59:17 -0800 | Subject | Re: smp_call_function_single lockups | From | Linus Torvalds <> |
| |
On Thu, Feb 19, 2015 at 8:32 AM, Rafael David Tinoco <inaddy@ubuntu.com> wrote: > Feb 19 08:21:28 derain kernel: [ 3.637682] Switched APIC routing to > cluster x2apic.
Ok. That "cluster x2apic" mode is just about the nastiest mode when it comes to sending a single ipi. We do that insane dance where we
- turn single cpu number into cpumask - copy the cpumask to a percpu temporary storage - walk each cpu in the cpumask - for each cpu, look up the cluster siblings - for each cluster sibling that is also in the cpumask, look up the logical apic mask and add it to the actual ipi destination mask - send an ipi to that final mask.
which is just insane. It's complicated, it's fragile, and it's unnecessary.
If we had a simple "send_IPI()" function, we could do this all with something much saner, and it would look sopmething like
static void x2apic_send_IPI(int cpu, int vector) { u32 dest = per_cpu(x86_cpu_to_logical_apicid, cpu); x2apic_wrmsr_fence(); __x2apic_send_IPI_dest(dest, vector, APIC_DEST_LOGICAL); }
and then 'void native_send_call_func_single_ipi()' would just look like
void native_send_call_func_single_ipi(int cpu) { apic->send_IPI(cpu, CALL_FUNCTION_SINGLE_VECTOR); }
but I might have missed something (and we might want to have a wrapper that says "if the apic doesn't have a 'send_IPI' function, use "send_IPI_mask(cpumask_of(cpu, vector) instead"
The fact that you need that no_x2apic_optout (which in turn means that your ACPI tables seem to say "don't use x2apic") also makes me worry.
Are there known errata for the x2apic?
Linus
| |