[Xen-devel] Re: [PATCH] linux/x86: eliminate nesting of run-queue locks inside xtime_lock

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Tue, 2010-08-10 at 15:10 +0100, Jan Beulich wrote:
> From: Zdenek Salvet <salvet@xxxxxxxxxxx>
> 
> According to Debian bug 591362 this has been causing problems. While
> no proof was given that the inverse lock order does actually occur
> anywhere (with interrupts enabled), it is plain unnecessary to take
> the risk.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

I'm right in thinking this is for traditional Xen/Linux kernel only,
aren't I?

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> 
> --- a/arch/i386/kernel/time-xen.c
> +++ b/arch/i386/kernel/time-xen.c
> @@ -666,6 +666,7 @@ irqreturn_t timer_interrupt(int irq, voi
>       s64 delta, delta_cpu, stolen, blocked;
>       u64 sched_time;
>       unsigned int i, cpu = smp_processor_id();
> +     int schedule_clock_was_set_work = 0;
>       struct shadow_time_info *shadow = &per_cpu(shadow_time, cpu);
>       struct vcpu_runstate_info *runstate = &per_cpu(runstate, cpu);
>  
> @@ -720,12 +721,14 @@ irqreturn_t timer_interrupt(int irq, voi
>  
>       if (shadow_tv_version != HYPERVISOR_shared_info->wc_version) {
>               update_wallclock();
> -             if (keventd_up())
> -                     schedule_work(&clock_was_set_work);
> +             schedule_clock_was_set_work = 1;
>       }
>  
>       write_sequnlock(&xtime_lock);
>  
> +     if (schedule_clock_was_set_work && keventd_up())
> +             schedule_work(&clock_was_set_work);
> +
>       /*
>        * Account stolen ticks.
>        * HACK: Passing NULL to account_steal_time()
> 
> 
> 



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