From: Joe Perches <joe@perches.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] printk: Add best-effort printk() buffering.
Date: Sun, 30 Apr 2017 09:11:56 -0700 [thread overview]
Message-ID: <1493568716.1874.7.camel@perches.com> (raw)
In-Reply-To: <1493560477-3016-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
On Sun, 2017-04-30 at 22:54 +0900, Tetsuo Handa wrote:
> Sometimes we want to printk() multiple lines in a group without being
> disturbed by concurrent printk() from interrupts and/or other threads.
> For example, mixed printk() output of multiple thread's dump makes it
> hard to interpret.
>
> This patch introduces fixed-sized statically allocated buffers for
> buffering printk() output for each thread/context in best effort
> (i.e. up to PAGE_SIZE bytes, up to 16 concurrent printk() users).
[]
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
[]
> +#define MAX_PRINTK_BUFFERS 16
> +static struct printk_buffer {
> + unsigned long context; /* printk_context() */
> + unsigned int nested;
> + unsigned int used; /* Valid bytes in buf[]. */
> + char buf[PAGE_SIZE];
> +} printk_buffers[MAX_PRINTK_BUFFERS];
Perhaps these buffers could be acquired by
alloc_page rather than be static structures and
the sizeof buf[PAGE_SIZE] should be reduced by
sizeof(unsigned long) +
sizeof(unsigned int) +
sizeof(unsigned int)
so that struct printk_buffers is exactly
PAGE_SIZE.
next prev parent reply other threads:[~2017-04-30 16:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-30 13:54 [PATCH] printk: Add best-effort printk() buffering Tetsuo Handa
2017-04-30 16:11 ` Joe Perches [this message]
2017-05-03 6:21 ` Tetsuo Handa
2017-05-03 9:30 ` Joe Perches
2017-05-08 7:05 ` Sergey Senozhatsky
2017-05-08 13:05 ` Tetsuo Handa
2017-05-09 1:04 ` Sergey Senozhatsky
2017-05-09 11:41 ` Tetsuo Handa
2017-05-10 6:21 ` Sergey Senozhatsky
2017-05-10 11:27 ` Tetsuo Handa
2017-05-15 13:15 ` Petr Mladek
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