netdev - Re: [PATCH] alx: add a simple AR816x/AR817x device driver

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Message-ID: <20130613230341.GB16632@electric-eye.fr.zoreil.com>
Date:	Fri, 14 Jun 2013 01:03:41 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	netdev@...r.kernel.org, mcgrof@...not-panic.com, kvalo@...rom.com,
	adrian.chadd@...il.com
Subject: Re: [PATCH] alx: add a simple AR816x/AR817x device driver

Johannes Berg <johannes@...solutions.net> :
[...]
> Yes, I suppose I could, but is it worth it? It's held only for a very
> short amount of time to get the indirect register access correct. I
> don't really see any reason to prefer a mutex here?

Neither a spinlock nor a mutex should be needed but I have to sleep
before figuring it.

> Not sure what you mean by "push it in the common core methods"? I
> actually suspect that this lock can't ever be contended because the
> callers hold the RTNL anyway, but I don't really want to rely on just
> that.

Don't be shy :o)

[...]
> Hmm, yeah, I'll have to think about that. I don't really care about the
> performance all that much ... just want the device to work :-)

Ok. It's fine.

> Would I really want to rely on NAPI for error interrupts and the like
> though? I thought NAPI could potentially be deferred due to budget etc.

It will have to wait for ksoftirqd once its budget is exhausted.

If the irq and napi handlers don't share a lock, either they are racing
or the napi handler will be kicked on irq return.

I'll admit a bias towards some extra latency if it can buy user context
comfort.

-- 
Ueimor
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