From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [RFC][PATCH 0/2] Access console drivers list under console_sem
Date: Wed, 24 Apr 2019 14:43:05 +0900 [thread overview]
Message-ID: <20190424054305.GA28894@jagdpanzerIV> (raw)
In-Reply-To: <20190423094801.377b8059@gandalf.local.home>
On (04/23/19 09:48), Steven Rostedt wrote:
> > RFC
> >
> > Normally, we grab console_sem lock before we iterate consoles
> > list, which is necessary if we want to be race free. The only exception
> > to this rule is console_flush_on_panic(). However, it seems that we are
> > not fully race free - register_console() iterates console drivers list
> > in unsafe manner in several places. E.g. the following scenarion:
> >
> > CPU0 CPU1
> > register_console() unregister_console()
> > console_lock()
> > for_each_console() // modify console_drivers
> > con->foo kfree(con)
> >
> > So I have two quick-n-dirty patches, which remove unsafe console list
> > access.
> >
> > What do you think?
>
> I just skimmed the patches and haven't done a thorough review, but the
> concept seems sane to me.
Thank you Steven. Let me know if anything doesn't work for you.
I have vague memories of a kernel Oops at con->foo dereferencing
(saw a message on linux-rt-users list a while ago, if I'm not
mistaken). And it seems that we have some races in printk code.
-ss
prev parent reply other threads:[~2019-04-24 5:43 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 6:25 [RFC][PATCH 0/2] Access console drivers list under console_sem Sergey Senozhatsky
2019-04-23 6:25 ` [RFC][PATCH 1/2] printk: lock console_sem before we unregister boot consoles Sergey Senozhatsky
2019-04-24 14:49 ` Petr Mladek
2019-04-25 3:52 ` Sergey Senozhatsky
2019-04-25 6:43 ` Sergey Senozhatsky
2019-04-25 9:20 ` Petr Mladek
2019-04-25 16:05 ` Steven Rostedt
2019-04-25 7:50 ` Petr Mladek
2019-04-25 7:56 ` Sergey Senozhatsky
2019-04-25 9:37 ` Sergey Senozhatsky
2019-04-23 6:25 ` [RFC][PATCH 2/2] printk: take console_sem when accessing console drivers list Sergey Senozhatsky
2019-04-24 15:13 ` Petr Mladek
2019-04-25 5:19 ` Sergey Senozhatsky
2019-04-25 6:47 ` Sergey Senozhatsky
2019-04-25 8:53 ` Petr Mladek
2019-04-23 13:48 ` [RFC][PATCH 0/2] Access console drivers list under console_sem Steven Rostedt
2019-04-24 5:43 ` Sergey Senozhatsky [this message]
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