linux-kernel - Re: Full dynticks needs evtdesc set before marking cpu online.

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Date:	Mon, 13 May 2013 07:55:14 -0500
From:	Robin Holt <holt@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Robin Holt <holt@....com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: Full dynticks needs evtdesc set before marking cpu online.

On Mon, May 13, 2013 at 11:21:00AM +0200, Thomas Gleixner wrote:
> On Wed, 8 May 2013, Robin Holt wrote:
> 
> > Thomas,
> > 
> > We are seeing failures booting medium sized machines which I think is
> > a change in expectations that dyntick put on x86's start_secondary.
> > 
> > During boot of cpus, we see an occassional panic in tick_do_broadcast at
> 
> http://lkml.indiana.edu/hypermail/linux/kernel/1305.0/01818.html
> 
> Will hit Linus tree soon.

I think this is really due to a sequence in start_secondary.  The cpu
has been marked as online, but its evtdesc has not been initialized.
I sent a followup to this with a hack/patch.

It was essentially:
--- linux.orig/arch/x86/kernel/smpboot.c
+++ linux/arch/x86/kernel/smpboot.c
@@ -264,6 +264,8 @@ notrace static void __cpuinit start_seco
         */
        check_tsc_sync_target();
 
+       x86_cpuinit.setup_percpu_clockev();
+
        /*
         * We need to hold vector_lock so there the set of online cpus
         * does not change while we are assigning vectors to cpus.  Holding
@@ -281,8 +283,6 @@ notrace static void __cpuinit start_seco
        /* to prevent fake stack check failure in clock setup */
        boot_init_stack_canary();
 
-       x86_cpuinit.setup_percpu_clockev();
-
        wmb();
        cpu_startup_entry(CPUHP_ONLINE);
 }


Robin
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