netdev - Re: [PATCH RFC] spinlock: split out debugging check from spin_lock

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Message-ID: <20130422201246.GA20687@hmsreliant.think-freely.org>
Date:	Mon, 22 Apr 2013 16:12:46 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Bart Van Assche <bart.vanassche@...il.com>
Cc:	Bart Van Assche <bvanassche@....org>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH RFC] spinlock: split out debugging check from
 spin_lock_mutex

On Thu, Apr 18, 2013 at 03:29:12PM -0400, Neil Horman wrote:
> Well, I guess Ingo doesn't have time  to respond here.  Given that, I've been
> looking at other ways of adressing this problem (as the more I think about it,
> the more I think changing mutex semantics, even to be more accepting, is going
> to be met with lots of friction).  I've come up with the below change, and it
> works well for me (I've hammered it with ifup/downs while sending messages over
> netconsole for 24 hours now without any incident).  I'm not sure I like all the
> details yet (I modified the rx_flag field to be a gneral flags field that uses
> test/set/clear_bit, which I don't think is necessecary, but it seems saner to
> me).  the meat of the change though is that instead of a mutex, we use two flags
> that, respectively, inhibit netpoll usage, and indicate when we're in a netpoll
> service path.  Using these two flags, in conjunction with a wait_queue, we can
> signal to executors in the netpoll path that we're inhibiting its use and expect
> to any user in the path to complete and wake up any contexts in the inhibiting
> path.  Seems to work well for me.  Let me know what you think, and I'll make any
> desired changes and post an official patch.
> 
> Best
> Neil
> 
Bart, any testing/thoughts here?  i'd like to get this fixed in the next few
days, but I'd like to get any feedback you might have first.

Neil

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