From: Jeff Layton <jlayton@redhat.com>
To: gchen <gang.chen@asianux.com>
Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [QUESTION] about NFS sub system between Public Kernel and Red Hat Kernel.
Date: Fri, 31 Aug 2012 07:02:13 -0700 [thread overview]
Message-ID: <20120831070213.6e350dd1@corrin.poochiereds.net> (raw)
In-Reply-To: <50404E40.3070702@asianux.com>
On Fri, 31 Aug 2012 13:40:16 +0800
gchen <gang.chen@asianux.com> wrote:
> Hi linux-nfs@vger.kernel.org
>
> I have 1 question, and also 2 conclusions which need confirm.
>
>
> 1) Question:
>
> Jeff Layton said in Red Hat Bugzilla (bug 848706):
> "Have configuration where the same host is acting as both NFS client
> and server. That's a configuration known to cause deadlocks."
>
> Does it mean that the public Linux kernel (not Red Hat) also can cause
> deadlocks if NFS client and server are under the same machine ?
>
Yes.
>
> 2) Confirm 1: (better by Jeff Layton)
>
> For function nfs_commit_set_lock in ./fs/nfs/write.c
>
> for latest public kernel version:
> the parameters of out_of_line_wait_on_bit_lock() are
> (&nfsi->flags, NFS_INO_COMMIT, nfs_wait_killable, TASK_KILLABLE)
> for Red Hat kernel version: kernel-2.6.18-308.4.1.el5
> the parameters of out_of_line_wait_on_bit_lock() are
> (&nfsi->flags, NFS_INO_COMMIT,
> nfs_wait_bit_uninterruptible, TASK_UNINTERRUPTIBLE)
>
> It means for red hat version:
> when deadlock occurs, we can not boot machine in normal way
> (it is true for my test machine, the deadlock task can not be killed)
> It means for public kernel version:
> "Assume deadlock occurs", we can still boot machine in normal way,
> because the task can be killed.
>
> Is what I said above correct ?
>
Not sure I understand your question. RHEL5 doesn't have support for
TASK_KILLABLE, and I didn't backport it, hence the difference in that
function.
>
> 3) Confirm 2:
>
> Is LTP (Linux Test Project) still a suitable test tools for public kernel ?
> (for ltp-full-20100331.gz stress test, it mounts NFS on local machine,
> and the latest LTP ltp-full-20120401.bz2 also seems the same).
>
That I'm not sure of. All I can tell you is that mounts over loopback
(or similar configurations) are easily deadlockable under load.
--
Jeff Layton <jlayton@redhat.com>
next prev parent reply other threads:[~2012-08-31 14:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-31 5:40 [QUESTION] about NFS sub system between Public Kernel and Red Hat Kernel gchen
2012-08-31 14:02 ` Jeff Layton [this message]
2012-09-02 5:41 ` gchen
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