linux-kernel - RE: [PATCH 11/13] irq debug: do not use print

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Date:   Mon, 11 Dec 2017 12:55:49 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Sergey Senozhatsky' <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@...linux.org.uk>,
        "Catalin Marinas" <catalin.marinas@....com>,
        Mark Salter <msalter@...hat.com>,
        "Tony Luck" <tony.luck@...el.com>,
        David Howells <dhowells@...hat.com>,
        "Yoshinori Sato" <ysato@...rs.sourceforge.jp>,
        Guan Xuetao <gxt@...c.pku.edu.cn>,
        Borislav Petkov <bp@...en8.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Vineet Gupta <vgupta@...opsys.com>,
        Fengguang Wu <fengguang.wu@...el.com>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        Petr Mladek <pmladek@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-c6x-dev@...ux-c6x.org" <linux-c6x-dev@...ux-c6x.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        "linux-am33-list@...hat.com" <linux-am33-list@...hat.com>,
        "linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: RE: [PATCH 11/13] irq debug: do not use print_symbol()

From: Sergey Senozhatsky
> Sent: 11 December 2017 12:50
> print_symbol() uses extra stack space to sprintf() symbol
> information and then to feed that buffer to printk()
> 
>   char buffer[KSYM_SYMBOL_LEN];
> 
>   sprint_symbol(buffer, address);
>   printk(fmt, buffer);
> 
> Replace print_symbol() with a direct printk("%pS") call.
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/irq/debug.h | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/irq/debug.h b/kernel/irq/debug.h
> index 17f05ef8f575..5766e15c1160 100644
> --- a/kernel/irq/debug.h
> +++ b/kernel/irq/debug.h
...
> @@ -15,13 +13,13 @@ static inline void print_irq_desc(unsigned int irq, struct irq_desc *desc)
>  	printk("irq %d, desc: %p, depth: %d, count: %d, unhandled: %d\n",
>  		irq, desc, desc->depth, desc->irq_count, desc->irqs_unhandled);
>  	printk("->handle_irq():  %p, ", desc->handle_irq);
> -	print_symbol("%s\n", (unsigned long)desc->handle_irq);
> +	pr_cont("%pS\n", desc->handle_irq);

Looks like you can (and should) use a single printk() instead of pr_cont.

	David