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From:   John Ogness <john.ogness@linutronix.de>
To:     Petr Mladek <pmladek@suse.com>
Cc:     linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Daniel Wang <wonderfly@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Jiri Slaby <jslaby@suse.com>,
        Peter Feiner <pfeiner@google.com>,
        linux-serial@vger.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [RFC PATCH v1 04/25] printk-rb: add writer interface
References: <20190212143003.48446-1-john.ogness@linutronix.de>
        <20190212143003.48446-5-john.ogness@linutronix.de>
        <20190214151650.5y337yy2jnnztsc6@pathway.suse.cz>
        <87ef8aosby.fsf@linutronix.de>
Date:   Fri, 15 Feb 2019 02:19:50 +0100
In-Reply-To: <87ef8aosby.fsf@linutronix.de> (John Ogness's message of "Fri, 15
        Feb 2019 00:36:49 +0100")
Message-ID: <87a7ixq24p.fsf@linutronix.de>
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On 2019-02-15, John Ogness <john.ogness@linutronix.de> wrote:
> prb_commit() does not actually care what is in the handle. It is going
> to commit everything up to the reserve.

After thinking about what I wrote here, I realized that the struct
prb_handle has no purpose in this ringbuffer implementation. We really
could simplify the writer interface to:

    char *prb_reserve(struct printk_ringbuffer *rb, unsigned int size);

    void prb_commit(struct printk_ringbuffer *rb);

That probably feels really strange because the writer doesn't specify
_what_ to commit. But this ringbuffer implementation doesn't need to
know that.

The only reason I can think of for having a handle is if there should be
any statistics, debugging, or sanity checking added. (For example if a
writer tried to commit something it did not reserve.)

John Ogness