Date: Wed, 18 Jan 2006 14:00:56 -0800 (PST)
Message-Id: <20060118.140056.39962680.davem@davemloft.net>
To: stern@rowland.harvard.edu
Cc: bcrl@kvack.org, akpm@osdl.org, sekharan@us.ibm.com, kaos@sgi.com,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/8] Notifier chain update
From: "David S. Miller" <davem@davemloft.net>
In-Reply-To: <Pine.LNX.4.44L0.0601181656430.4974-100000@iolanthe.rowland.org>
References: <20060118214204.GG16285@kvack.org>
	<Pine.LNX.4.44L0.0601181656430.4974-100000@iolanthe.rowland.org>
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From: Alan Stern <stern@rowland.harvard.edu>
Date: Wed, 18 Jan 2006 16:57:30 -0500 (EST)

> On Wed, 18 Jan 2006, Benjamin LaHaise wrote:
> 
> > A notifier callee should not be sleeping, if anything it should be putting 
> > its work onto a workqueue and completing it when it gets scheduled if it 
> > has to do something that blocks.
> 
> Sez who?  If it's not documented in the kernel source, I don't believe 
> it.

Many notifiers even get run from software interrupt context,
making sleeping illegal.

For example, IPV6 addresses can get added/removed from a device
in response to packets, and these operations trigger the
inet6addr_chain notifier in net/ipv6/addrconf.c

So sleeping in a notifier is indeed illegal.
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