[PATCH 2/16] xics: update default_server during migrate_irqs_away
Nathan Fontenot
nfont at austin.ibm.com
Tue Oct 14 07:04:22 EST 2008
Milton Miller wrote:
> Currently, every time we determine which irq server to use, we check if
> default_server, which is the id of the bootcpu, is still online. But
> default_server is a hardware cpu, not the logical cpu id needed to index
> cpu_online_map.
>
> Since the default server can only go offline during a cpu hotplug event,
> explicitly check the default server and choose the new one when we move
> irqs away from the cpu being offlined.
>
> This has the added benefit of only needing the boot_cpuid to be updated
> and not relying on the cpu being marked offline during migrate_irqs_away.
>
> Also, since xics_update_irq_servers only reads device tree information, we
> can call it before xics_init_host in xics_init_IRQ and then default_server
> will always be valid when we can reach get_irq_server via the host ops.
>
> Signed-off-by: Milton Miller <miltonm at bga.com>
Acked-by: Nathan Fontenot <nfont at austin.ibm.com>
> ---
> I realized the hard vs soft cpu id as I was writing the patch description.
> get_irq_server is called from unmask and set affinity.
>
> The effects of this bug would be the increased pathlength to walk the
> device tree in the unmask and set affinity methods, and possible failure
> to migrate irqs during cpu hotplug removal (not likely to be seen on
> until a sequence of remove and adds is performed).
>
> This check dates to 2.6.25 via de0723dcca6e593a12a259798a54eb0e82628fb8.
>
> Index: next.git/arch/powerpc/platforms/pseries/xics.c
> ===================================================================
> --- next.git.orig/arch/powerpc/platforms/pseries/xics.c 2008-10-04 16:36:07.000000000 -0500
> +++ next.git/arch/powerpc/platforms/pseries/xics.c 2008-10-04 16:36:09.000000000 -0500
> @@ -208,9 +208,6 @@ static int get_irq_server(unsigned int v
> cpumask_t cpumask = irq_desc[virq].affinity;
> cpumask_t tmp = CPU_MASK_NONE;
>
> - if (! cpu_isset(default_server, cpu_online_map))
> - xics_update_irq_servers();
> -
> if (!distribute_irqs)
> return default_server;
>
> @@ -685,8 +682,8 @@ void __init xics_init_IRQ(void)
> if (found == 0)
> return;
>
> - xics_init_host();
> xics_update_irq_servers();
> + xics_init_host();
>
> if (firmware_has_feature(FW_FEATURE_LPAR))
> ppc_md.get_irq = xics_get_irq_lpar;
> @@ -779,6 +776,10 @@ void xics_migrate_irqs_away(void)
> int cpu = smp_processor_id(), hw_cpu = hard_smp_processor_id();
> unsigned int irq, virq;
>
> + /* If we used to be the default server, move to the new "boot_cpuid" */
> + if (hw_cpu == default_server)
> + xics_update_irq_servers();
> +
> /* Reject any interrupt that was queued to us... */
> xics_set_cpu_priority(0);
>
More information about the Linuxppc-dev
mailing list