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!)
>
WARNING: multiple messages have this Message-ID (diff)
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>, Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linux-ext4@vger.kernel.org
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!)
>
next prev parent reply other threads:[~2009-06-22 1:34 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-10 5:42 [PATCH 00/11] [GIT PULL] more updates for the tag format Steven Rostedt
2009-06-10 5:42 ` [PATCH 01/11] tracing/events: convert block trace points to TRACE_EVENT(), fix Steven Rostedt
2009-06-10 5:42 ` [PATCH 02/11] tracing: add nsec2sec print formats Steven Rostedt
2009-06-10 5:42 ` [PATCH 03/11] tracing: convert lockdep lock_acquired trace point to use nsec2usec tag Steven Rostedt
2009-06-10 5:42 ` [PATCH 04/11] tracing: add major and minor tags for print format Steven Rostedt
2009-06-10 5:42 ` [PATCH 05/11] tracing: use << to print < instead of \< Steven Rostedt
2009-06-10 5:42 ` [PATCH 06/11] tracing: convert the block trace points to use the new tag format Steven Rostedt
2009-06-10 5:42 ` [PATCH 07/11] tracing: add test for strings in event " Steven Rostedt
2009-06-10 5:42 ` [PATCH 08/11] tracing: add func and symfunc to " Steven Rostedt
2009-06-10 7:48 ` Frederic Weisbecker
2009-06-10 12:55 ` Steven Rostedt
2009-06-10 5:42 ` [PATCH 09/11] tracing: check full name for field Steven Rostedt
2009-06-10 5:42 ` [PATCH 10/11] tracing: update sample code with new tag format Steven Rostedt
2009-06-10 5:42 ` [PATCH 11/11] tracing: move > to out of macros and into print statement Steven Rostedt
2009-06-10 9:26 ` [PATCH 00/11] [GIT PULL] more updates for the tag format Ingo Molnar
2009-06-10 11:11 ` Frédéric Weisbecker
2009-06-10 13:01 ` Theodore Tso
2009-06-10 13:49 ` Steven Rostedt
2009-06-10 14:39 ` Mathieu Desnoyers
2009-06-10 15:21 ` Steven Rostedt
2009-06-10 16:03 ` Theodore Tso
2009-06-10 16:17 ` Steven Rostedt
2009-06-11 13:03 ` Christoph Hellwig
2009-06-11 15:47 ` Theodore Tso
2009-06-11 17:14 ` Frederic Weisbecker
2009-06-11 19:20 ` Theodore Tso
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]
2009-06-22 1:36 ` Li Zefan
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