linux-kernel - Re: [PATCH] x86/nmi: Use raw lock

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Message-ID: <20170725162255.qeduzogbzqu5al5m@redhat.com>
Date:   Tue, 25 Jul 2017 12:22:55 -0400
From:   Don Zickus <dzickus@...hat.com>
To:     Scott Wood <swood@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/nmi: Use raw lock

On Mon, Jul 24, 2017 at 04:32:42PM -0500, Scott Wood wrote:
> register_nmi_handler() can be called from PREEMPT_RT atomic context
> (e.g. wakeup_cpu_via_init_nmi() or native_stop_other_cpus()), and thus
> ordinary spinlocks cannot be used.

Yeah, I guess we have a few awkward places where we register an nmi handler.

Acked-by: Don Zickus <dzickus@...hat.com>


> 
> Signed-off-by: Scott Wood <swood@...hat.com>
> ---
>  arch/x86/kernel/nmi.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
> index 446c8aa09b9b..35aafc95e4b8 100644
> --- a/arch/x86/kernel/nmi.c
> +++ b/arch/x86/kernel/nmi.c
> @@ -39,26 +39,26 @@
>  #include <trace/events/nmi.h>
>  
>  struct nmi_desc {
> -	spinlock_t lock;
> +	raw_spinlock_t lock;
>  	struct list_head head;
>  };
>  
>  static struct nmi_desc nmi_desc[NMI_MAX] = 
>  {
>  	{
> -		.lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[0].lock),
> +		.lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[0].lock),
>  		.head = LIST_HEAD_INIT(nmi_desc[0].head),
>  	},
>  	{
> -		.lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[1].lock),
> +		.lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[1].lock),
>  		.head = LIST_HEAD_INIT(nmi_desc[1].head),
>  	},
>  	{
> -		.lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[2].lock),
> +		.lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[2].lock),
>  		.head = LIST_HEAD_INIT(nmi_desc[2].head),
>  	},
>  	{
> -		.lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[3].lock),
> +		.lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[3].lock),
>  		.head = LIST_HEAD_INIT(nmi_desc[3].head),
>  	},
>  
> @@ -163,7 +163,7 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action)
>  
>  	init_irq_work(&action->irq_work, nmi_max_handler);
>  
> -	spin_lock_irqsave(&desc->lock, flags);
> +	raw_spin_lock_irqsave(&desc->lock, flags);
>  
>  	/*
>  	 * Indicate if there are multiple registrations on the
> @@ -181,7 +181,7 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action)
>  	else
>  		list_add_tail_rcu(&action->list, &desc->head);
>  	
> -	spin_unlock_irqrestore(&desc->lock, flags);
> +	raw_spin_unlock_irqrestore(&desc->lock, flags);
>  	return 0;
>  }
>  EXPORT_SYMBOL(__register_nmi_handler);
> @@ -192,7 +192,7 @@ void unregister_nmi_handler(unsigned int type, const char *name)
>  	struct nmiaction *n;
>  	unsigned long flags;
>  
> -	spin_lock_irqsave(&desc->lock, flags);
> +	raw_spin_lock_irqsave(&desc->lock, flags);
>  
>  	list_for_each_entry_rcu(n, &desc->head, list) {
>  		/*
> @@ -207,7 +207,7 @@ void unregister_nmi_handler(unsigned int type, const char *name)
>  		}
>  	}
>  
> -	spin_unlock_irqrestore(&desc->lock, flags);
> +	raw_spin_unlock_irqrestore(&desc->lock, flags);
>  	synchronize_rcu();
>  }
>  EXPORT_SYMBOL_GPL(unregister_nmi_handler);
> -- 
> 1.8.3.1
>