On 11/07/18 13:06, Jan Beulich wrote:
> In order to be able to service #MC on offlined CPUs, GDT, IDT, stack,
For clarity, I'd phrase this as "CPUs, the GDT, ..." to help visually
separate CPUs as it isn't a part of the rest of the list.
> --- a/xen/arch/x86/genapic/x2apic.c
> +++ b/xen/arch/x86/genapic/x2apic.c
> @@ -201,18 +201,25 @@ static int update_clusterinfo(
> if ( !cluster_cpus_spare )
> cluster_cpus_spare = xzalloc(cpumask_t);
> if ( !cluster_cpus_spare ||
> - !alloc_cpumask_var(&per_cpu(scratch_mask, cpu)) )
> + !cond_alloc_cpumask_var(&per_cpu(scratch_mask, cpu)) )
> err = -ENOMEM;
> break;
> case CPU_UP_CANCELED:
> case CPU_DEAD:
> + case CPU_REMOVE:
> + if ( park_offline_cpus == (action != CPU_REMOVE) )
> + break;
> if ( per_cpu(cluster_cpus, cpu) )
> {
> cpumask_clear_cpu(cpu, per_cpu(cluster_cpus, cpu));
> if ( cpumask_empty(per_cpu(cluster_cpus, cpu)) )
> + {
> xfree(per_cpu(cluster_cpus, cpu));
> + per_cpu(cluster_cpus, cpu) = NULL;
> + }
> }
> free_cpumask_var(per_cpu(scratch_mask, cpu));
> + clear_cpumask_var(&per_cpu(scratch_mask, cpu));
freeing and NULL-ing the pointer at the same time is already a common
pattern How about introducing
/* Free an allocation, and zero the pointer to it. */
#define XFREE(p)
({
typeof(*p) *_p = (p);
xfree(_p);
_p = NULL;
})
and a similar wrapper for FREE_CPUMASK_VAR(p) which takes care of the
NULL-ing as well?
In time as these start to get used more widely, it should reduce the
chances of double-freeing in cleanup paths.
> @@ -63,6 +63,8 @@ static cpumask_t scratch_cpu0mask;
> cpumask_t cpu_online_map __read_mostly;
> EXPORT_SYMBOL(cpu_online_map);
>
> +bool __read_mostly park_offline_cpus;
> +
> unsigned int __read_mostly nr_sockets;
> cpumask_t **__read_mostly socket_cpumask;
> static cpumask_t *secondary_socket_cpumask;
> @@ -887,7 +889,7 @@ static void cleanup_cpu_root_pgt(unsigne
> }
> }
>
> -static void cpu_smpboot_free(unsigned int cpu)
> +static void cpu_smpboot_free(unsigned int cpu, bool all)
Perhaps "remove" or "remove_cpu", to match the CPU_REMOVE terminology?
Also, we probably want a comment here explaining the difference between
parking and removing in terms of what infrastructure needs to remain valid.
~Andrew
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