linux-kernel - Re: 2.6.24-rc5-mm1 -- inconsistent {in-softirq-W} -> {softirq-on-R} usage.

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Message-Id: <20071216.135939.00534238.davem@davemloft.net>
Date:	Sun, 16 Dec 2007 13:59:39 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	akpm@...ux-foundation.org
Cc:	miles.lane@...il.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, mingo@...e.hu, a.p.zijlstra@...llo.nl
Subject: Re: 2.6.24-rc5-mm1 -- inconsistent {in-softirq-W} ->
 {softirq-on-R} usage.

From: Andrew Morton <akpm@...ux-foundation.org>
Date: Fri, 14 Dec 2007 15:36:33 -0800

> The networking bug looks to be around sock_i_ino()'s taking of
> sk_callback_lock with softirq's enabled.  Perhaps this will fix it.

One should be suspicious of any case where write_lock is performed
on sk->sk_callback_lock in softint context.  And that's the only
way this can trigger, so this patch is wrong.

Generally, sock_orphan() and sock_graft() are the only primary
places where sk->sk_callback_lock is acquired as a writer.  And
these should be invoked only from process context.

Perhaps there is some exception to this in some specialized layer such
as SUNRPC, which are the only other spots I see potentially doing
sk->sk_callback_lock write acquires in softint context, which as
stated should not be done.

OCFS2 and ISCSI seem to be following the rules in it's write lock
calls on this lock.
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