On 18/03/2019 13:11, Juergen Gross wrote:
> cpu_disable_scheduler() is being called from __cpu_disable() today.
> There is no need to call it on the cpu just being disabled, so use
> the CPU_DEAD case of the cpu notifier chain.
>
> Signed-off-by: Juergen Gross <jgr...@suse.com>
> ---
> xen/arch/x86/smpboot.c | 3 ---
> xen/common/schedule.c | 12 +++++-------
> 2 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
> index 7d1226d7bc..b7a0a4a419 100644
> --- a/xen/arch/x86/smpboot.c
> +++ b/xen/arch/x86/smpboot.c
> @@ -1221,9 +1221,6 @@ void __cpu_disable(void)
> cpumask_clear_cpu(cpu, &cpu_online_map);
> fixup_irqs(&cpu_online_map, 1);
> fixup_eoi();
> -
> - if ( cpu_disable_scheduler(cpu) )
> - BUG();
> }
It looks like ARM needs an equivalent adjustment.
>
> void __cpu_die(unsigned int cpu)
> diff --git a/xen/common/schedule.c b/xen/common/schedule.c
> index 60755a631e..665747f247 100644
> --- a/xen/common/schedule.c
> +++ b/xen/common/schedule.c
> @@ -773,8 +773,9 @@ void restore_vcpu_affinity(struct domain *d)
> }
>
> /*
> - * This function is used by cpu_hotplug code from stop_machine context
> + * This function is used by cpu_hotplug code via cpu notifier chain
> * and from cpupools to switch schedulers on a cpu.
> + * Caller must get domlist_read_lock.
s/get/hold/ ?
With at least the ARM side adjusted, Reviewed-by: Andrew Cooper
<andrew.coop...@citrix.com>
> */
> int cpu_disable_scheduler(unsigned int cpu)
> {
> @@ -789,12 +790,6 @@ int cpu_disable_scheduler(unsigned int cpu)
> if ( c == NULL )
> return ret;
>
> - /*
> - * We'd need the domain RCU lock, but:
> - * - when we are called from cpupool code, it's acquired there already;
> - * - when we are called for CPU teardown, we're in stop-machine context,
> - * so that's not be a problem.
> - */
> for_each_domain_in_cpupool ( d, c )
> {
> for_each_vcpu ( d, v )
> @@ -1738,6 +1733,9 @@ static int cpu_schedule_callback(
> rc = cpu_schedule_up(cpu);
> break;
> case CPU_DEAD:
> + rcu_read_lock(&domlist_read_lock);
> + cpu_disable_scheduler(cpu);
> + rcu_read_unlock(&domlist_read_lock);
> SCHED_OP(sched, deinit_pdata, sd->sched_priv, cpu);
> /* Fallthrough */
> case CPU_UP_CANCELED:
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