linux-kernel - Re: [RFC][PATCHv5 6/7] printk: use printk

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Date:   Mon, 12 Dec 2016 17:30:18 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>,
        Tejun Heo <tj@...nel.org>, Calvin Owens <calvinowens@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCHv5 6/7] printk: use printk_safe buffers in printk

On Thu 2016-12-01 22:55:45, Sergey Senozhatsky wrote:
> Use printk_safe per-CPU buffers in printk recursion-prone blocks:
> -- around logbuf_lock protected sections in vprintk_emit() and
>    console_unlock()
> -- around down_trylock_console_sem() and up_console_sem()
> 
> Note that this solution addresses deadlocks caused by printk()
> recursive calls only. That is vprintk_emit() and console_unlock().
> 
> Another thing to note is that we now keep lockdep enabled in printk,
> because we are protected against the printk recursion caused by lockdep
> in vprintk_emit() by the printk-safe mechanism - we first switch to
> per-CPU buffers and only then access the deadlock-prone locks.
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

Looks fine and safe to me.

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr