linux-kernel - Re: INFO: suspicious rcu_dereference_check() usage - kernel/pid.c:419 invoked rcu_dereference

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Message-ID: <20101110160211.GA2562@redhat.com>
Date:	Wed, 10 Nov 2010 17:02:11 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Greg Thelen <gthelen@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Jens Axboe <axboe@...nel.dk>
Subject: Re: INFO: suspicious rcu_dereference_check() usage -
	kernel/pid.c:419 invoked rcu_dereference_check() without protection!

(another try with the proper email address)

On 11/09, Paul E. McKenney wrote:
>
> Thank you, Oleg!  Greg, would you be willing to update your patch
> to remove the comment?  (Perhaps tasklist_lock as well...)

Agreed, I think tasklock should be killed.


But wait. Whatever we do, isn't this code racy? I do not see why, say,
sys_ioprio_set(IOPRIO_WHO_PROCESS) can't install ->io_context after
this task has already passed exit_io_context().

Jens, am I missed something?

Oleg.

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