linux-kernel - Re: [PATCH v6 1/3] printk: Add line-buffered printk() API.

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Message-ID: <20181102144028.GQ10491@bombadil.infradead.org>
Date:   Fri, 2 Nov 2018 07:40:28 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexander Potapenko <glider@...gle.com>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v6 1/3] printk: Add line-buffered printk() API.

On Fri, Nov 02, 2018 at 10:31:55PM +0900, Tetsuo Handa wrote:
>   get_printk_buffer() tries to assign a "struct printk_buffer" from
>   statically preallocated array. get_printk_buffer() returns NULL if
>   all "struct printk_buffer" are in use, but the caller does not need to
>   check for NULL.

This seems like a great way of wasting 16kB of memory.  Since you've
already made printk_buffered() work with a NULL initial argument, what's
the advantage over just doing kmalloc(1024, GFP_ATOMIC)?