linux-kernel - Re: [PATCH 2/2] kdb: Call vkdb_printf() from vprintk

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Date:   Sun, 23 Oct 2016 22:23:43 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] kdb: Call vkdb_printf() from vprintk_default() only
 when wanted

On (10/21/16 14:50), Petr Mladek wrote:
[..]
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index d5e397315473..db73e33811e7 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1941,7 +1941,9 @@ int vprintk_default(const char *fmt, va_list args)
>  	int r;
>  
>  #ifdef CONFIG_KGDB_KDB
> -	if (unlikely(kdb_trap_printk)) {
> +	/* Allow to pass printk() to kdb but avoid a recursion. */
> +	if (unlikely(kdb_trap_printk &&
> +		     kdb_printf_cpu != smp_processor_id())) {
					^^^^^
		aren't we are in preemptible here?

	-ss

>  		r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
>  		return r;