linux-kernel - Re: [RFC][PATCH 0/6] Use printk_safe context for TTY and UART port locks

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Date:   Wed, 20 Jun 2018 11:56:41 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        SergeySenozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC][PATCH 0/6] Use printk_safe context for TTY and UART port
 locks

On (06/19/18 22:34), Steven Rostedt wrote:
> 
> > There is no valid reason why an UART driver should do a printk() of
> > any sort inside the critical region where the console is locked.
> > 
> > Just remove those printk's, don't add new crazy locking.
> 
> Perhaps we should do an audit of the console drivers and remove all
> printk, pr_* , WARN*, BUG* from them.

I think I did a terrible job explaining my motivation.

Sorry for that!


What I tried to address with my patch set was not a direct uart->printk,
but mostly all those

        uart-> tty / core kernel / who knows what else -> printk

cases. When are in that special context "called from uart driver" which
can backfire on us.

	-ss