linux-kernel - Re: [RFC][PATCH 7/7] printk: new printk() recursion detection

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Message-ID: <20160930020045.GD547@swordfish>
Date:   Fri, 30 Sep 2016 11:00:45 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Jan Kara <jack@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, Calvin Owens <calvinowens@...com>,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCH 7/7] printk: new printk() recursion detection

On (09/29/16 15:19), Petr Mladek wrote:
> I am sorry but I do not understand this much. printk() should set the
> alternative implementation in the critical section by default.
> Why do we need to handle this so specially?
> 
> Is it because of flushing in NMI context when panicing? I would call
> vprintk_emit() directly from the flush_line() function in this case.
> Then all other possible error printk's will get redirected to the
> NMI buffer which is good enouh.

I'm going to re-do the entire thing. I had some cases in mind, like
WARN from vsnprintf from printk from alt_printk_flushing from panic.
or something like this. perhaps too complicated, will re-think it.

	-ss