Re: [PATCH v2] printk: Use the main logbuf in NMI when logbuf_lock is available

From	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] printk: Use the main logbuf in NMI when logbuf_lock is available
Date	2017-05-05 04:30 +0200
Message-ID	<tDBah-3LK-1@gated-at.bofh.it> (permalink)
References	<tDraV-5t6-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On (05/04/17 17:46), Petr Mladek wrote:
[..]
> Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Signed-off-by: Petr Mladek <pmladek@suse.com>

Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

a small nitpick,

[..]
>  void printk_nmi_enter(void)
>  {
> -	this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
> +	/*
> +	 * The size of the extra per-CPU buffer is limited. Use it only when
> +	 * the main one is locked. If this CPU is not in the safe context,
> +	 * the lock must be taken on another CPU and we could wait for it.
> +	 */
> +	if (raw_spin_is_locked(&logbuf_lock) &&
> +	    this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) {
> +		this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);

could we please check `printk_context' (local to a particular CPU)
first and, if positive, then access `logbuf_lock' (which is global)?

	-ss

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[PATCH v2] printk: Use the main logbuf in NMI when logbuf_lock is available Petr Mladek <pmladek@suse.com> - 2017-05-04 17:50 +0200
  Re: [PATCH v2] printk: Use the main logbuf in NMI when logbuf_lock  is available Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-05-05 04:30 +0200

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