netdev - RE: [PATCH] igb: completely disable interrupts during netpoll

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Message-ID: <36D9DB17C6DE9E40B059440DB8D95F52057B3FE5@orsmsx418.amr.corp.intel.com>
Date:	Thu, 26 Jun 2008 00:23:59 -0700
From:	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
To:	"David Miller" <davem@...emloft.net>, <andy@...yhouse.net>
Cc:	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"Allan, Bruce W" <bruce.w.allan@...el.com>,
	"Ronciak, John" <john.ronciak@...el.com>, <netdev@...r.kernel.org>
Subject: RE: [PATCH] igb: completely disable interrupts during netpoll

David Miller wrote:
> It's better to have a good understanding of why the deadlocks
> happen, and this was decidedly missing from your commit message.
> 
> NAPI is designed in such a way that if pending interrupts arrive
> after NAPI disables chip interrupts it should be handled just
> fine and in fact I see this happen all the time on some of my
> test systems.

I think the deadlocks occur (only when using netpoll) because the tx
cleanup (igb_clean_tx_irq) is being called simultaneously from two
routines, which generally is guaranteed not to happen in regular
everyday napi mode because of the bh_disable before calling dev->poll.


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