linux-kernel - Re: spi: Add call to spi_slave_abort() function when spidev driver is released

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Date:   Fri, 27 Sep 2019 00:38:49 +0200
From:   Lukasz Majewski <lukma@...x.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Colin Ian King <colin.king@...onical.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: spi: Add call to spi_slave_abort() function when spidev driver
 is released

Hi Mark, Geert,

> On Thu, Sep 26, 2019 at 04:06:45PM +0200, Lukasz Majewski wrote:
> > > On Thu, Sep 26, 2019 at 2:49 PM Lukasz Majewski <lukma@...x.de>
> > > wrote:  
> 
> > > > The question is if we shall call the spi_slave_abort() when
> > > > cleaning up spi after releasing last reference, or each time
> > > > release callback is called ?    
> 
> > > TBH, I don't know.  Is it realistic that there are multiple
> > > opens?  
> 
> > I'm using on my setup only one test program to use /dev/spidevX.Y
> > and /dev/spidevA.B (loopback with wired connection).  
> 
> > However, you also shall be able to connect via ssh and run the same
> > setup in parallel...  
> 
> It doesn't seem entirely realistic, but I can imagine cases like
> fork()/exec() where we end up with two copies of the file open
> but end up immediately closing one.
> 
> > > That means the abort is called only for the last user.
> > > And only if the underlying device still exists.  Which means that
> > > if it has disappeared (how can that happen? spidev unbind?),  
> 
> > In my case, I just disconnect some SPI signals and the test program
> > just hangs. I do need to ctrl+c to stop it (or use timeout).   
> 
> > From my debugging the .release callback is called each time the
> > program is aborted (either with ctrl+c or timeout).  
> 
> Should be on file close IIRC.

Any ideas on how to solve this issue?

Maybe, it would be sufficient for now to move the spi_slave_abort() in
spi_release() before we decrease (spidev->users--) the use count?


Best regards,

Lukasz Majewski

--

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