Re: [PATCH] percpu data: only iterate over possible CPUs

[Eric Dumazet]

Rik van Riel a écrit :
> On Sun, 5 Feb 2006, Linux Kernel Mailing List wrote:
>
> > [PATCH] percpu data: only iterate over possible CPUs
>
> This sched.c bit breaks Xen, and probably also other architectures
> that have CPU hotplug.  I suspect the reason is that during early 
> bootup only the boot CPU is online, so nothing initialises the
> runqueues for CPUs that are brought up afterwards.
>
> I suspect we can get rid of this problem quite easily by moving
> runqueue initialisation to init_idle()...

Please fix Xen to match include/linux/cpumask.h documentation that says :

/*
 * The following particular system cpumasks and operations manage
 * possible, present and online cpus.  Each of them is a fixed size
 * bitmap of size NR_CPUS.
 *
 *  #ifdef CONFIG_HOTPLUG_CPU
 *     cpu_possible_map - all NR_CPUS bits set
 *     cpu_present_map  - has bit 'cpu' set iff cpu is populated
 *     cpu_online_map   - has bit 'cpu' set iff cpu available to scheduler
 *  #else
 *     cpu_possible_map - has bit 'cpu' set iff cpu is populated
 *     cpu_present_map  - copy of cpu_possible_map
 *     cpu_online_map   - has bit 'cpu' set iff cpu available to scheduler
 *  #endif
 */



Eric
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