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Groups > linux.kernel > #1724644 > unrolled thread

[PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional

Started byKees Cook <keescook@chromium.org>
First post2017-09-01 01:40 +0200
Last post2017-09-01 20:00 +0200
Articles 5 — 3 participants

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  [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional Kees Cook <keescook@chromium.org> - 2017-09-01 01:40 +0200
    Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization  unconditional Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-01 07:10 +0200
    Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization  unconditional Ian Abbott <abbotti@mev.co.uk> - 2017-09-01 11:40 +0200
      Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization  unconditional Ian Abbott <abbotti@mev.co.uk> - 2017-09-01 11:40 +0200
        Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional Kees Cook <keescook@chromium.org> - 2017-09-01 20:00 +0200

#1724644 — [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional

FromKees Cook <keescook@chromium.org>
Date2017-09-01 01:40 +0200
Subject[PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional
Message-ID<ukHe1-3XZ-1@gated-at.bofh.it>
With timer initialization made unconditional, there is no reason to
make del_timer_sync() calls conditionally, there by removing the test
of the .data field.

Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: devel@driverdev.osuosl.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/staging/comedi/drivers/das16.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/comedi/drivers/das16.c b/drivers/staging/comedi/drivers/das16.c
index 5d157951f63f..4514179b2007 100644
--- a/drivers/staging/comedi/drivers/das16.c
+++ b/drivers/staging/comedi/drivers/das16.c
@@ -941,10 +941,8 @@ static void das16_alloc_dma(struct comedi_device *dev, unsigned int dma_chan)
 	/* DMA uses two buffers */
 	devpriv->dma = comedi_isadma_alloc(dev, 2, dma_chan, dma_chan,
 					   DAS16_DMA_SIZE, COMEDI_ISADMA_READ);
-	if (devpriv->dma) {
-		setup_timer(&devpriv->timer, das16_timer_interrupt,
-			    (unsigned long)dev);
-	}
+	setup_timer(&devpriv->timer, das16_timer_interrupt,
+		    (unsigned long)dev);
 }
 
 static void das16_free_dma(struct comedi_device *dev)
@@ -952,8 +950,7 @@ static void das16_free_dma(struct comedi_device *dev)
 	struct das16_private_struct *devpriv = dev->private;
 
 	if (devpriv) {
-		if (devpriv->timer.data)
-			del_timer_sync(&devpriv->timer);
+		del_timer_sync(&devpriv->timer);
 		comedi_isadma_free(devpriv->dma);
 	}
 }
-- 
2.7.4

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#1724784 — Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional

FromGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Date2017-09-01 07:10 +0200
SubjectRe: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional
Message-ID<ukMnp-7GJ-25@gated-at.bofh.it>
In reply to#1724644
On Thu, Aug 31, 2017 at 04:29:38PM -0700, Kees Cook wrote:
> With timer initialization made unconditional, there is no reason to
> make del_timer_sync() calls conditionally, there by removing the test
> of the .data field.
> 
> Cc: Ian Abbott <abbotti@mev.co.uk>
> Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: devel@driverdev.osuosl.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  drivers/staging/comedi/drivers/das16.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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#1724909 — Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional

FromIan Abbott <abbotti@mev.co.uk>
Date2017-09-01 11:40 +0200
SubjectRe: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional
Message-ID<ukQAF-21R-13@gated-at.bofh.it>
In reply to#1724644
On 01/09/17 00:29, Kees Cook wrote:
> With timer initialization made unconditional, there is no reason to
> make del_timer_sync() calls conditionally, there by removing the test
> of the .data field.
> 
> Cc: Ian Abbott <abbotti@mev.co.uk>
> Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: devel@driverdev.osuosl.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>   drivers/staging/comedi/drivers/das16.c | 9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/comedi/drivers/das16.c b/drivers/staging/comedi/drivers/das16.c
> index 5d157951f63f..4514179b2007 100644
> --- a/drivers/staging/comedi/drivers/das16.c
> +++ b/drivers/staging/comedi/drivers/das16.c
> @@ -941,10 +941,8 @@ static void das16_alloc_dma(struct comedi_device *dev, unsigned int dma_chan)
>   	/* DMA uses two buffers */
>   	devpriv->dma = comedi_isadma_alloc(dev, 2, dma_chan, dma_chan,
>   					   DAS16_DMA_SIZE, COMEDI_ISADMA_READ);
> -	if (devpriv->dma) {
> -		setup_timer(&devpriv->timer, das16_timer_interrupt,
> -			    (unsigned long)dev);
> -	}
> +	setup_timer(&devpriv->timer, das16_timer_interrupt,
> +		    (unsigned long)dev);
>   }

das16_alloc_dma() returns before the call to comedi_isadma_alloc() if 
the dma_chan parameter is not one of the values 1 or 3, so setup_timer() 
will not be called in that case.

>   
>   static void das16_free_dma(struct comedi_device *dev)
> @@ -952,8 +950,7 @@ static void das16_free_dma(struct comedi_device *dev)
>   	struct das16_private_struct *devpriv = dev->private;
>   
>   	if (devpriv) {
> -		if (devpriv->timer.data)
> -			del_timer_sync(&devpriv->timer);
> +		del_timer_sync(&devpriv->timer);

If setup_timer() has not been called (see remark above), this change 
will break.

>   		comedi_isadma_free(devpriv->dma);
>   	}
>   }
> 


-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@mev.co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-

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#1724916 — Re: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional

FromIan Abbott <abbotti@mev.co.uk>
Date2017-09-01 11:40 +0200
SubjectRe: [PATCH 26/31] staging/comedi/das16: Make timer initialization unconditional
Message-ID<ukQAG-21R-31@gated-at.bofh.it>
In reply to#1724909
On 01/09/17 10:29, Ian Abbott wrote:
> On 01/09/17 00:29, Kees Cook wrote:
>> With timer initialization made unconditional, there is no reason to
>> make del_timer_sync() calls conditionally, there by removing the test
>> of the .data field.
>>
>> Cc: Ian Abbott <abbotti@mev.co.uk>
>> Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: devel@driverdev.osuosl.org
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>>   drivers/staging/comedi/drivers/das16.c | 9 +++------
>>   1 file changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/staging/comedi/drivers/das16.c 
>> b/drivers/staging/comedi/drivers/das16.c
>> index 5d157951f63f..4514179b2007 100644
>> --- a/drivers/staging/comedi/drivers/das16.c
>> +++ b/drivers/staging/comedi/drivers/das16.c
>> @@ -941,10 +941,8 @@ static void das16_alloc_dma(struct comedi_device 
>> *dev, unsigned int dma_chan)
>>       /* DMA uses two buffers */
>>       devpriv->dma = comedi_isadma_alloc(dev, 2, dma_chan, dma_chan,
>>                          DAS16_DMA_SIZE, COMEDI_ISADMA_READ);
>> -    if (devpriv->dma) {
>> -        setup_timer(&devpriv->timer, das16_timer_interrupt,
>> -                (unsigned long)dev);
>> -    }
>> +    setup_timer(&devpriv->timer, das16_timer_interrupt,
>> +            (unsigned long)dev);
>>   }
> 
> das16_alloc_dma() returns before the call to comedi_isadma_alloc() if 
> the dma_chan parameter is not one of the values 1 or 3, so setup_timer() 
> will not be called in that case.
> 
>>   static void das16_free_dma(struct comedi_device *dev)
>> @@ -952,8 +950,7 @@ static void das16_free_dma(struct comedi_device *dev)
>>       struct das16_private_struct *devpriv = dev->private;
>>       if (devpriv) {
>> -        if (devpriv->timer.data)
>> -            del_timer_sync(&devpriv->timer);
>> +        del_timer_sync(&devpriv->timer);
> 
> If setup_timer() has not been called (see remark above), this change 
> will break.
> 
>>           comedi_isadma_free(devpriv->dma);
>>       }
>>   }
>>

If you want to avoid testing devpriv->timer.data for some reason, you 
could make the calls to setup_timer() and del_timer_sync() depend on 
devpriv->dma.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@mev.co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-

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#1725267

FromKees Cook <keescook@chromium.org>
Date2017-09-01 20:00 +0200
Message-ID<ukYoy-8lL-5@gated-at.bofh.it>
In reply to#1724916
On Fri, Sep 1, 2017 at 2:38 AM, Ian Abbott <abbotti@mev.co.uk> wrote:
> On 01/09/17 10:29, Ian Abbott wrote:
>>
>> On 01/09/17 00:29, Kees Cook wrote:
>>>
>>> With timer initialization made unconditional, there is no reason to
>>> make del_timer_sync() calls conditionally, there by removing the test
>>> of the .data field.
>>>
>>> Cc: Ian Abbott <abbotti@mev.co.uk>
>>> Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Cc: devel@driverdev.osuosl.org
>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>> ---
>>>   drivers/staging/comedi/drivers/das16.c | 9 +++------
>>>   1 file changed, 3 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/staging/comedi/drivers/das16.c
>>> b/drivers/staging/comedi/drivers/das16.c
>>> index 5d157951f63f..4514179b2007 100644
>>> --- a/drivers/staging/comedi/drivers/das16.c
>>> +++ b/drivers/staging/comedi/drivers/das16.c
>>> @@ -941,10 +941,8 @@ static void das16_alloc_dma(struct comedi_device
>>> *dev, unsigned int dma_chan)
>>>       /* DMA uses two buffers */
>>>       devpriv->dma = comedi_isadma_alloc(dev, 2, dma_chan, dma_chan,
>>>                          DAS16_DMA_SIZE, COMEDI_ISADMA_READ);
>>> -    if (devpriv->dma) {
>>> -        setup_timer(&devpriv->timer, das16_timer_interrupt,
>>> -                (unsigned long)dev);
>>> -    }
>>> +    setup_timer(&devpriv->timer, das16_timer_interrupt,
>>> +            (unsigned long)dev);
>>>   }
>>
>>
>> das16_alloc_dma() returns before the call to comedi_isadma_alloc() if the
>> dma_chan parameter is not one of the values 1 or 3, so setup_timer() will
>> not be called in that case.
>>
>>>   static void das16_free_dma(struct comedi_device *dev)
>>> @@ -952,8 +950,7 @@ static void das16_free_dma(struct comedi_device *dev)
>>>       struct das16_private_struct *devpriv = dev->private;
>>>       if (devpriv) {
>>> -        if (devpriv->timer.data)
>>> -            del_timer_sync(&devpriv->timer);
>>> +        del_timer_sync(&devpriv->timer);
>>
>>
>> If setup_timer() has not been called (see remark above), this change will
>> break.
>>
>>>           comedi_isadma_free(devpriv->dma);
>>>       }
>>>   }
>>>
>
> If you want to avoid testing devpriv->timer.data for some reason, you could
> make the calls to setup_timer() and del_timer_sync() depend on devpriv->dma.

Thanks for checking this! I think the cleanest would be to just move
setup_timer() to the start of das16_alloc_dma(). I'll make that
adjustment.

-Kees

-- 
Kees Cook
Pixel Security

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