linux-kernel - Re: [bisected] rcu_sched detected stalls - 4.15 or newer kernel with some Xeon skylake CPUs and extended APIC

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Date:   Thu, 17 May 2018 11:59:42 -0400
From:   Rick Warner <rick@...roway.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [bisected] rcu_sched detected stalls - 4.15 or newer kernel with
 some Xeon skylake CPUs and extended APIC

Success!

This resolved the issue.  Thanks Thomas!

Rick

On 05/17/18 08:36, Thomas Gleixner wrote:
> Rick,
>
> On Wed, 16 May 2018, Rick Warner wrote:
>
>> I've attached the dmesg output with the kernel parameter and supplied patch.
> Thanks for providing the data. I think I know what's wrong here. Does the
> patch below fix your problem?
>
> While you test, I go looking for a big brown paperbag.
>
> Thanks,
>
> 	tglx
>
> 8<----------------
>
> --- a/arch/x86/kernel/apic/x2apic_cluster.c
> +++ b/arch/x86/kernel/apic/x2apic_cluster.c
> @@ -124,6 +124,7 @@ static void init_x2apic_ldr(void)
>  			goto update;
>  	}
>  	cmsk = cluster_hotplug_mask;
> +	cmsk->clusterid = cluster;
>  	cluster_hotplug_mask = NULL;
>  update:
>  	this_cpu_write(cluster_masks, cmsk);