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

[Eric Dumazet <dada1@cosmosbay.com>]

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