linux-kernel - Re: [PATCH printk v4 11/39] console: introduce wrappers to read/write console flags

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Message-ID: <Y3OFk2n7BquPUkOf@alley>
Date:   Tue, 15 Nov 2022 13:26:59 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH printk v4 11/39] console: introduce wrappers to
 read/write console flags

On Mon 2022-11-14 17:35:04, John Ogness wrote:
> After switching to SRCU for console list iteration, some readers
> will begin readings console->flags as a data race. Locklessly
> reading console->flags provides a consistent value because there
> is at most one CPU modifying console->flags and that CPU is
> using only read-modify-write operations.
> 
> Introduce a wrapper for SRCU iterators to read console flags.
> Introduce a matching wrapper to write to flags of registered
> consoles. Writing to flags of registered consoles is synchronized
> by the console_list_lock.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr