linux-kernel - Re: [PATCH 2/3] iio: stmpe-adc: Make wait

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Date:   Tue, 7 May 2019 14:31:49 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "jic23@...nel.org" <jic23@...nel.org>,
        "David.Laight@...LAB.COM" <David.Laight@...LAB.COM>
CC:     "stefan@...er.ch" <stefan@...er.ch>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        Max Krummenacher <max.krummenacher@...adex.com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "knaack.h@....de" <knaack.h@....de>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>
Subject: Re: [PATCH 2/3] iio: stmpe-adc: Make wait_completion non
 interruptible

On Tue, 2019-05-07 at 08:23 +0000, David Laight wrote:
> From: Jonathan Cameron
> > Sent: 05 May 2019 16:44
> > On Fri, 3 May 2019 15:58:38 +0000
> > Philippe Schenker <philippe.schenker@...adex.com> wrote:
> > 
> > > On Fri, 2019-05-03 at 14:39 +0000, David Laight wrote:
> > > > From: Philippe Schenker
> > > > > Sent: 03 May 2019 14:57
> > > > > In some cases, the wait_completion got interrupted. This caused the
> > > > > error-handling to mutex_unlock the function. The before turned on
> > > > > interrupt then got called anyway. In the ISR then completion()
> > > > > was called causing problems.
> > > > > 
> > > > > Making this wait_completion non interruptible solves the problem.
> > > > 
> > > > Won't the same thing happen if the interrupt occurs just after
> > > > the timeout?
> > > > 
> > > > 	David
> > > > 
> > > > 
> > > > -
> > > > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes,
> > > > MK1 1PT,
> > > > UK
> > > > Registration No: 1397386 (Wales)
> > > > 
> > > 
> > > You're of course right... Thanks for pointing this out. I will send a v2
> > > with a
> > > better solution then.
> > > 
> > 
> > Isn't the timeout long enough that it should only happen if the hardware has
> > a fault? If that's the case, I wouldn't worry too much about possibility of
> > an interrupt causing confusion as long as it isn't catastrophic.
> 
> The 'confusion' is likely to be 'catastrophic' unless the code is written
> to handle it properly.
> 
> Cancelling callbacks is hard to get right and often not done properly.
> Timing out an interrupt is much the same problem.
> 
> 	David

I sorted it out now, there where also some more bugs I found and corrected.

@Jonathan: I will send a completely new series of patches that will include
patch 3/3 from this series but not the one you already applied. This due to
increased patch number and different order...
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT,
> UK
> Registration No: 1397386 (Wales)
>