From: Li Zefan <lizf@cn.fujitsu.com>
To: Theodore Tso <tytso@mit.edu>, Li Zefan <lizf@cn.fujitsu.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
I
Subject: Re: [BUG] bugs in jbd2_dev_to_name() (was Re: [PATCH 00/11] [GIT PULL] more updates for the tag format)
Date: Mon, 22 Jun 2009 09:36:28 +0800 [thread overview]
Message-ID: <4A3EE01C.5090600@cn.fujitsu.com> (raw)
In-Reply-To: <20090619123204.GC31377@mit.edu>
Theodore Tso wrote:
> On Fri, Jun 19, 2009 at 04:14:23PM +0800, Li Zefan wrote:
>>> rcu_read_lock();
>>> if (devcache[i] && devcache[i]->device == device) {
>>> ret = devcache[i]->devname;
>>> rcu_read_unlock();
>>> return ret;
>> It doesn't seem safe to dereference @ret outside rcu read section.
>
> Note the comments at the beginning of the function:
>
Ah, I overlooked the comments.
But the patch that adds rcu locking around trace event prints
never gets merged:
http://lkml.org/lkml/2009/4/15/549
Steven?
> The caller should use rcu_read_lock() in order to make sure the
> device name stays valid until its done with it. We use
> rcu_read_lock() as well to make sure we're safe in case the caller
> gets sloppy, and because rcu_read_lock() is cheap and can be safely
> nested.
>
> I suppose I should change the wording to indicate that it adds a bit
> more safety (as in, the crash won't happen inside this function, but
> as far as the caller is concerned, all bets are off!)
>
prev parent reply other threads:[~2009-06-22 1:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20090610054206.510574695@goodmis.org>
[not found] ` <20090610092644.GA20889@elte.hu>
[not found] ` <c62985530906100411o5a178352n53f7d247f6e9dba9@mail.gmail.com>
[not found] ` <20090610130127.GA6647@mit.edu>
[not found] ` <alpine.DEB.2.00.0906100911190.30552@gandalf.stny.rr.com>
[not found] ` <20090610160303.GA10240@mit.edu>
[not found] ` <20090611130318.GB14220@infradead.org>
[not found] ` <20090611154751.GD9275@mit.edu>
[not found] ` <20090611171434.GA6011@nowhere>
[not found] ` <20090611192037.GA5116@mit.edu>
2009-06-19 8:14 ` [BUG] bugs in jbd2_dev_to_name() (was Re: [PATCH 00/11] [GIT PULL] more updates for the tag format) Li Zefan
2009-06-19 12:32 ` Theodore Tso
2009-06-22 1:36 ` Li Zefan [this message]
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