linux-kernel - Re: [PATCHv3 1/3] NETPOLL: Extend rx

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Message-ID: <1191723499.1820816.1330635848166.JavaMail.root@zimbra-prod-mbox-2.vmware.com>
Date:	Thu, 1 Mar 2012 13:04:08 -0800 (PST)
From:	Andrei Warkentin <awarkentin@...are.com>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrei Warkentin <andreiw@...are.com>,
	kgdb-bugreport@...ts.sourceforge.net,
	Matt Mackall <mpm@...enic.com>,
	Andrei Warkentin <andrey.warkentin@...il.com>
Subject: Re: [PATCHv3 1/3] NETPOLL: Extend rx_hook support.

----- Original Message -----
> From: "Andrei Warkentin" <awarkentin@...are.com>
> To: "Jason Wessel" <jason.wessel@...driver.com>
> Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, "Andrei Warkentin" <andreiw@...are.com>,
> kgdb-bugreport@...ts.sourceforge.net, "Matt Mackall" <mpm@...enic.com>, "Andrei Warkentin"
> <andrey.warkentin@...il.com>
> Sent: Tuesday, February 28, 2012 12:43:52 PM
> Subject: Re: [PATCHv3 1/3] NETPOLL: Extend rx_hook support.
> 
> > 
> > All that netpoll_poll() did was to call netpoll_poll_dev().  I have
> > not yet looked at the differences between kgdboe and the netkdb
> > code
> > you proposed but I would have suspected it also falls victim to the
> > ethernet preemption problem which prevented kgdboe from ever being
> > considered for a mainline merge.  Certainly there are ways to fix
> > this
> > problem but most involved changes to scheduling, core net code, or
> > substantial driver specific changes.
> > 
> 
> I see, I read up on the issues w.r.t. preemption. Could this be
> worked
> around by modifiying affected drivers to bypass locking if they are
> used in KDB context? Make some accessor netdev-specific lock/unlocks
> that won't do anything if running in KDB context.
> 
>

By the way, is there a good way to repro the preemption case? Hopefully this doesn't
involve some crazy hardware...

A
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