From: David Howells <dhowells@redhat.com>
To: paulmck@linux.vnet.ibm.com
Cc: dhowells@redhat.com,
Linus Torvalds <torvalds@linux-foundation.org>,
Jiri Olsa <jolsa@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Eric Dumazet <eric.dumazet@gmail.com>,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH] cred - synchronize rcu before releasing cred
Date: Thu, 29 Jul 2010 09:34:20 +0100 [thread overview]
Message-ID: <30107.1280392460@redhat.com> (raw)
In-Reply-To: <20100729060004.GD2447@linux.vnet.ibm.com>
Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> It is perfectly legal for an RCU callback to invoke call_rcu(). However,
> this should be used -only- to wait for RCU readers. If there are no
> RCU readers, the callback might be re-invoked in very short order,
> expecially on UP systems.
>
> Or am I misunderstanding what you mean by "require call_rcu() to be
> able to cope iwth requeueing"?
I mean for call_rcu() to be called on an object that's already been
call_rcu()'d but not yet processed.
For example if struct cred gets its usage count reduced to 0, __put_cred()
will call_rcu() it, but what happens if someone comes along and resurrects it
by increasing its usage count again? And what happens if the usage count is
reduced back to zero and __put_cred() calls call_rcu() again before
put_cred_rcu() has a chance to run?
David
next prev parent reply other threads:[~2010-07-29 8:35 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-27 15:50 [PATCH] cred - synchronize rcu before releasing cred Jiri Olsa
2010-07-27 16:16 ` Linus Torvalds
2010-07-27 16:46 ` David Howells
2010-07-27 17:56 ` Linus Torvalds
2010-07-28 8:25 ` Jiri Olsa
2010-07-28 12:07 ` David Howells
2010-07-28 12:47 ` David Howells
2010-07-29 6:00 ` Paul E. McKenney
2010-07-29 8:34 ` David Howells [this message]
2010-07-30 21:32 ` Paul E. McKenney
2010-07-28 13:17 ` David Howells
2010-07-28 14:46 ` Jiri Olsa
2010-07-29 9:38 ` Jiri Olsa
2010-07-28 15:51 ` Linus Torvalds
-- strict thread matches above, loose matches on Subject: below --
2010-06-25 13:33 Jiri Olsa
2010-07-02 12:14 ` Jiri Olsa
2010-06-16 12:24 Jiri Olsa
2010-06-16 12:45 ` Eric Dumazet
2010-06-16 12:57 ` Jiri Olsa
2010-06-16 13:10 ` Eric Dumazet
2010-06-16 16:08 ` Jiri Olsa
2010-06-17 23:50 ` David Howells
2010-06-19 12:01 ` Jiri Olsa
2010-06-25 12:55 ` Jiri Olsa
2010-06-25 13:28 ` David Howells
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