linux-kernel - Re: [PATCH 28/51] arm64, hw_breakpoint.c: Fix CPU hotplug callback registration

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Date:	Thu, 6 Feb 2014 11:41:02 +0000
From:	Will Deacon <will.deacon@....com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	"paulus@...ba.org" <paulus@...ba.org>,
	"oleg@...hat.com" <oleg@...hat.com>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"tj@...nel.org" <tj@...nel.org>,
	"walken@...gle.com" <walken@...gle.com>,
	"ego@...ux.vnet.ibm.com" <ego@...ux.vnet.ibm.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 28/51] arm64, hw_breakpoint.c: Fix CPU hotplug callback
 registration

On Wed, Feb 05, 2014 at 10:09:45PM +0000, Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:

[...]

> Fix the hw-breakpoint code in arm64 by using this latter form of callback
> registration.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
> 
>  arch/arm64/kernel/hw_breakpoint.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
> index f17f581..24e88d0 100644
> --- a/arch/arm64/kernel/hw_breakpoint.c
> +++ b/arch/arm64/kernel/hw_breakpoint.c
> @@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void)
>  	pr_info("found %d breakpoint and %d watchpoint registers.\n",
>  		core_num_brps, core_num_wrps);
>  
> +	cpu_maps_update_begin();
> +
>  	/*
>  	 * Reset the breakpoint resources. We assume that a halting
>  	 * debugger will leave the world in a nice state for us.
> @@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void)
>  			      TRAP_HWBKPT, "hw-watchpoint handler");
>  
>  	/* Register hotplug notifier. */
> -	register_cpu_notifier(&hw_breakpoint_reset_nb);
> +	__register_cpu_notifier(&hw_breakpoint_reset_nb);
> +
> +	cpu_maps_update_done();
> +
>  	/* Register cpu_suspend hw breakpoint restore hook */
>  	cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);

  Acked-by: Will Deacon <will.deacon@....com>

Will
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