* kernelfans@xxxxxxxxx <kernelfans@xxxxxxxxx> [2014-10-16 15:29:50]:
> Some system such as powerpc, some tsk (vcpu thread) can only run on
> the dedicated cpu. Since we adapt some asymmetric method to monitor the
> whole physical cpu. (powerKVM only allows the primary hwthread to
> set up runtime env for the secondary when entering guest).
>
> Nowadays, powerKVM run with all the secondary hwthread offline to ensure
> the vcpu threads only run on the primary thread. But we plan to keep all
> cpus online when running powerKVM to give more power when switching back
> to host, so introduce sys_allowed cpumask to reflect the cpuset which
> the vcpu thread can run on.
>
> Signed-off-by: Liu Ping Fan <pingfank@xxxxxxxxxxxxxxxxxx>
> ---
> include/linux/init_task.h | 1 +
> include/linux/sched.h | 6 ++++++
> kernel/sched/core.c | 10 ++++++++--
> 3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/init_task.h b/include/linux/init_task.h
> index 2bb4c4f3..c56f69e 100644
> --- a/include/linux/init_task.h
> +++ b/include/linux/init_task.h
> @@ -172,6 +172,7 @@ extern struct task_group root_task_group;
> .normal_prio = MAX_PRIO-20, \
> .policy = SCHED_NORMAL, \
> .cpus_allowed = CPU_MASK_ALL, \
> + .sys_allowed = CPU_MASK_ALL, \
Do we really need another mask, cant we just use cpus_allowed itself.
> .nr_cpus_allowed= NR_CPUS, \
> .mm = NULL, \
> .active_mm = &init_mm, \
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 5c2c885..ce429f3 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1260,7 +1260,10 @@ struct task_struct {
>
> unsigned int policy;
> int nr_cpus_allowed;
> + /* Anded user and sys_allowed */
> cpumask_t cpus_allowed;
> + /* due to the feature of asymmetric, some tsk can only run on such cpu */
> + cpumask_t sys_allowed;
>
> #ifdef CONFIG_PREEMPT_RCU
> int rcu_read_lock_nesting;
> @@ -2030,6 +2033,9 @@ static inline void tsk_restore_flags(struct task_struct *task,
> }
>
> #ifdef CONFIG_SMP
> +extern void set_cpus_sys_allowed(struct task_struct *p,
> + const struct cpumask *new_mask);
> +
> extern void do_set_cpus_allowed(struct task_struct *p,
> const struct cpumask *new_mask);
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ec1a286..2cd1ae3 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4596,13 +4596,19 @@ void init_idle(struct task_struct *idle, int cpu)
> }
>
> #ifdef CONFIG_SMP
> +void set_cpus_sys_allowed(struct task_struct *p,
> + const struct cpumask *new_mask)
> +{
> + cpumask_copy(&p->sys_allowed, new_mask);
> +}
> +
This function doesnt seem to be used anywhere... Not sure why it is
introduced
> void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
> {
> if (p->sched_class && p->sched_class->set_cpus_allowed)
> p->sched_class->set_cpus_allowed(p, new_mask);
>
> - cpumask_copy(&p->cpus_allowed, new_mask);
> - p->nr_cpus_allowed = cpumask_weight(new_mask);
> + cpumask_and(&p->cpus_allowed, &p->sys_allowed, new_mask);
> + p->nr_cpus_allowed = cpumask_weight(&p->cpus_allowed);
> }
>
> /*
> --
> 1.8.3.1
>
>
--
Thanks and Regards
Srikar Dronamraju
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