netdev - Re: [PATCH] jme: netpoll support

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Message-ID: <1342670909.11373.105.camel@deadeye.wl.decadent.org.uk>
Date:	Thu, 19 Jul 2012 05:08:29 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Miller <davem@...emloft.net>
CC:	<cooldavid@...ldavid.org>, <lekensteyn@...il.com>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH] jme: netpoll support

On Wed, 2012-07-18 at 20:24 -0700, David Miller wrote:
> From: "Guo-Fu Tseng" <cooldavid@...ldavid.org>
> Date: Thu, 19 Jul 2012 10:00:10 +0800
> 
> > On Wed, 18 Jul 2012 09:45:24 -0700 (PDT), David Miller wrote
> >> From: Lekensteyn <lekensteyn@...il.com>
> >> Date: Tue, 17 Jul 2012 18:29:34 +0200
> >> 
> >> > From: Peter Wu <lekensteyn@...il.com>
> >> > 
> >> > This patch adds the netpoll function to support netconsole. Tested and works
> >> > fine on my "JMC250 PCI Express Gigabit Ethernet Controller" (PCI ID 0250).
> >> > 
> >> > Signed-off-by: Peter Wu <lekensteyn@...il.com>
> >> 
> >> Applied to net-next
> >> 
> >> I really wonder if this driver works on SMP systems at all.
> > Hi davem:
> > 
> > I wrote/tested this driver on SMP system at very beginning.
> > In face some of the design was aimed for SMP systems.
> > Is there any obvious bug or something I should be aware of?
> 
> Well, you do no locking in your IRQ handler.
> 
> So how can you be sure in jme_free_irq() during jme_close() that the
> handler is not running on some cpu somewhere?
> 
> That's why drivers like drivers/net/ethernet/broadcom/tg3.c have
> a function like tg3_irq_quiesce(), to guarentee that no code path
> is executing in the interrupt handler.

What on earth are you talking about?  You can never be sure of that with
shared IRQ handlers; so free_irq() wait if necessary.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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