linux-kernel - Re: [PATCH printk v2 33/38] printk: introduce console_list

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Message-ID: <Y1D+aPltJYNGhucW@kroah.com>
Date:   Thu, 20 Oct 2022 09:53:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH printk v2 33/38] printk: introduce console_list_lock

On Wed, Oct 19, 2022 at 05:01:55PM +0206, John Ogness wrote:
> Currently there exist races in console_register(), where the types
> of registered consoles are checked (without holding the console_lock)
> and then after acquiring the console_lock, it is assumed that the list
> has not changed. Also, some code that performs console_unregister()
> make similar assumptions.
> 
> Introduce a console_list_lock to provide full synchronization for any
> console list changes. The console_list_lock also provides
> synchronization for updates to console->flags.
> 
> Note that one of the various responsibilities of the console_lock is
> also intended to provide this synchronization. Later changes will
> update call sites relying on the console_lock for this purpose. Once
> all call sites have been updated, the console_lock will be relieved
> of synchronizing console_list and console->flags updates.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> ---
>  include/linux/console.h | 20 ++++++++--
>  kernel/printk/printk.c  | 82 +++++++++++++++++++++++++++++++++++------
>  2 files changed, 88 insertions(+), 14 deletions(-)

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>