linux-kernel - Re: [RFC PATCH v5 1/3] printk-rb: new printk ringbuffer implementation (writer)

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Message-ID: <87v9qpzxdi.fsf@linutronix.de>
Date:   Mon, 09 Dec 2019 10:00:57 +0100
From:   John Ogness <john.ogness@...utronix.de>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        kexec@...ts.infradead.org
Subject: Re: [RFC PATCH v5 1/3] printk-rb: new printk ringbuffer implementation (writer)

On 2019-12-09, Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> wrote:
>> +#define _DATA_SIZE(sz_bits)		(1UL << (sz_bits))
>> +#define _DESCS_COUNT(ct_bits)		(1U << (ct_bits))
>> +#define DESC_SV_BITS			(sizeof(int) * 8)
>> +#define DESC_COMMITTED_MASK		(1U << (DESC_SV_BITS - 1))
>
> What does SV state for? State Value?

Yes. Originally this thing was just called the state. But it was a bit
confusing in the code because there is also an enum desc_state (used for
state queries), which is _not_ the value that is stored in the state
variable. That's why the code is using state_var/state_val (SV) for the
actual data values, keeping it separate from desc_state/d_state for the
the state queries.

John Ogness