netdev - Re: [PATCH 2/2]: e1000: avoid lockup durig error recovery

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Date:	Wed, 7 Nov 2007 17:15:38 -0800
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	"Kok, Auke" <auke-jan.h.kok@...el.com>
Cc:	Linas Vepstas <linas@...tin.ibm.com>, wenxiong@...ibm.com,
	e1000-devel@...ts.sourceforge.net,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	john.ronciak@...el.com, jeffrey.t.kirsher@...el.com,
	Jeff Garzik <jeff@...zik.org>, NetDev <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2]: e1000: avoid lockup durig error recovery

On Wed, 07 Nov 2007 14:45:18 -0800
"Kok, Auke" <auke-jan.h.kok@...el.com> wrote:

> [adding netdev, jeff G to the Cc]
> 
> Linas Vepstas wrote:
> > On Wed, Nov 07, 2007 at 01:50:17PM -0800, Kok, Auke wrote:
> >> Linas Vepstas wrote:
> >>> If a PCI bus error is encountered during device open, the
> >>> error recovery routines will attempt to close the device.
> >>> If napi has not yet been enabled, the napi disable in the
> >>> close will hang. 
> >>>
> >>> Signed-off-by: Linas Vepstas <linas@...tin.ibm.com>
> >>>
> >>> ----
> >>> The "elegence" of this solution is arguable: one could
> >>> say its "better" to perform this check in e1000_down().
> >>> However, doing so will disrupt a commonly used path,
> >>> whereas here, the hack is in the infrequently used
> >>> error path, and thus less intrusive. 
> >>>

Same problem might be possible in suspend/resume.
The problem with testing napi_enabled is that state can get changed
by racing irq.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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