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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 27 Oct 2016 20:30:50 -0700
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Subject: Re: [RFC][PATCHv4 0/6] printk: use printk_safe to handle printk()
 recursive calls
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        Tejun Heo <tj@kernel.org>, Calvin Owens <calvinowens@fb.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Mel Gorman <mgorman@techsingularity.net>,
        Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
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        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
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On Thu, Oct 27, 2016 at 8:49 AM, Sergey Senozhatsky
<sergey.senozhatsky@gmail.com> wrote:
>
>         RFC
>
>         This patch set extends a lock-less NMI per-cpu buffers idea to
> handle recursive printk() calls. The basic mechanism is pretty much the
> same -- at the beginning of a deadlock-prone section we switch to lock-less
> printk callback, and return back to a default printk implementation at the
> end; the messages are getting flushed to a logbuf buffer from a safer
> context.

This looks very reasonable to me.

Does this also obviate the need for "printk_deferred()" that the
scheduler and the clock code uses?  Because that would be a lovely
thing to look at if it doesn't..

             LInus