linux-kernel - Re: linux.git: printk() problem

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Message-ID: <20161025044452.GA411@swordfish>
Date:   Tue, 25 Oct 2016 13:44:52 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Joe Perches <joe@...ches.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.cz>, Tejun Heo <tj@...nel.org>,
        Calvin Owens <calvinowens@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: linux.git: printk() problem

On (10/24/16 21:15), Linus Torvalds wrote:
[..]
> No. Most cont lines never hit the delay, because when the line is
> completed, it is flushed (and then printed synchronously, assuming it
> can get the console lock).
> 
> So the timeout only ever comes into effect if the line isn't completed
> in time at all. Which is actually very rare, and never happens for the
> "let's print things out in multiple chinks because we're using a
> loop".
> 
> Similarly, if a new printk() happens due to interleaving, the previous
> buffered line is always flushed first, so buffering never causes
> out-of-order behavior.

thanks. the patch works fine on my x86 box.

> Basically, the only time the timer actually does anything is if
> something just does a printk() without a newline, and no other
> printouts happen for the next 0.1s.

ok. perhaps, like slow serial console. will test on arm board later.

	-ss