From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.xen@gmail.com>
Subject: Re: [PATCH 1/2] x86/crash: Indicate how well
 nmi_shootdown_cpus() managed to do.
Date: Wed, 25 Sep 2013 06:56:22 +0100
Message-ID: <CE683996.5EFB8%keir.xen@gmail.com>
References: <1380052613-3837-1-git-send-email-andrew.cooper3@citrix.com>
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To: Andrew Cooper <andrew.cooper3@citrix.com>, Xen-devel <xen-devel@lists.xen.org>
Cc: Tim Deegan <tim@xen.org>, Jan Beulich <JBeulich@suse.com>
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On 24/09/2013 20:56, "Andrew Cooper" <andrew.cooper3@citrix.com> wrote:

> Having nmi_shootdown_cpus() report which pcpus failed to be shot down is a
> useful debugging hint as to what possibly went wrong (especially when the
> crash logs seem to indicate that an NMI timeout occurred while waiting for one
> of the problematic pcpus to perform an action).
> 
> This is achieved by swapping an atomic_t count of unreported pcpus with a
> cpumask.  In the case that the 1 second timeout occurs, use the cpumask to
> identify the problematic pcpus.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Tim Deegan <tim@xen.org>
> 
> ---
> 

> @@ -162,12 +164,22 @@ static void nmi_shootdown_cpus(void)
>      smp_send_nmi_allbutself();
>  
>      msecs = 1000; /* Wait at most a second for the other cpus to stop */
> -    while ( (atomic_read(&waiting_for_crash_ipi) > 0) && msecs )
> +    while ( (cpumask_weight(&waiting_to_crash) > 0) && msecs )
>      {
>          mdelay(1);
>          msecs--;
>      }
>  
> +    /* Leave a hint of how well we did trying to shoot down the other cpus */
> +    if ( msecs )

if (cpumask_empty(&waiting_to_crash))
Would be more obvious I think.

Apart from that
Acked-by: Keir Fraser <keir@xen.org>

> +        printk("Shot down all cpus\n");
> +    else
> +    {
> +        cpulist_scnprintf(keyhandler_scratch, sizeof keyhandler_scratch,
> +                          &waiting_to_crash);
> +        printk("Failed to shoot down cpus {%s}\n", keyhandler_scratch);
> +    }
> +
>      /* Crash shutdown any IOMMU functionality as the crashdump kernel is not
>       * happy when booting if interrupt/dma remapping is still enabled */
>      iommu_crash_shutdown();