linux-kernel - Re: [PATCH v2] printk/kdb: Redirect printk messages into kdb in any context

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Message-ID: <20200520111746.GB520@jagdpanzerIV.localdomain>
Date:   Wed, 20 May 2020 20:17:46 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Daniel Thompson <daniel.thompson@...aro.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Douglas Anderson <dianders@...omium.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>
Subject: Re: [PATCH v2] printk/kdb: Redirect printk messages into kdb in any
 context

On (20/05/20 12:22), Petr Mladek wrote:
> kdb has to get messages on consoles even when the system is stopped.
> It uses kdb_printf() internally and calls console drivers on its own.
> 
> It uses a hack to reuse an existing code. It sets "kdb_trap_printk"
> global variable to redirect even the normal printk() into the
> kdb_printf() variant.
> 
> The variable "kdb_trap_printk" is checked in printk_default() and
> it is ignored when printk is redirected to printk_safe in NMI context.
> Solve this by moving the check into printk_func().
> 
> It is obvious that it is not fully safe. But it does not make things
> worse. The console drivers are already called in this context by
> db_printf() direct calls.
> 
> Reported-by: Sumit Garg <sumit.garg@...aro.org>
> Tested-by: Sumit Garg <sumit.garg@...aro.org>
> Signed-off-by: Petr Mladek <pmladek@...e.com>

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

	-ss