linux-kernel - Re: [PATCH 1/2] prevent gpio chip drivers from unloading while used

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Date:	Sat, 9 Feb 2008 12:41:45 +0100 (CET)
From:	Guennadi Liakhovetski <g.liakhovetski@...gutronix.de>
To:	David Brownell <david-b@...bell.net>
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] prevent gpio chip drivers from unloading while used

On Fri, 8 Feb 2008, David Brownell wrote:

> > Yes, that's what I'm saying. I had a GPIO in use and rmmod-ed pca953x. It 
> > did produce an error message
> > 
> > pca953x 0-0041: gpiochip_remove() failed, -16
> > 
> > , but rmmod completed.
> 
> Doesn't that seem buglike to you?
> 
> Oh, right -- the module exit code will ignore that status, it doesn't
> even have a way to report failures any more.  Crap.
> 
> So it looks like we have no choice but to do this.  Can you make sure
> all the rmmod-capable gpio_chip drivers support this?  Ignore the SOC
> support, that never supports rmmod -- just the stuff in drivers/gpio.

As long as you find these two patches acceptable, I'll cook up an 
incremental patch to fix those.

> > AFAIU, the only 2 ways currently to prevent rmmod  
> > from completing, are: increment module use-count, then the respective 
> > module_exit() function is not called at all and rmmod fails with -EBUSY. 
> > Or block in rmmod until the resource becomes free. None of these has 
> > happened. BTW, I think, there's the same problem with i2c adapter drivers.
> 
> Right.  In fact, every time you'd expect driver removal errors to
> cause module removal to fail.   Maybe this is part of that whole
> "should we even *support* rmmod" discussion, which I tuned out.

We don't want to start another one here, do we?:-)

Thanks
Guennadi
---
Guennadi Liakhovetski
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