Re: [PATCH] irqdomain: protect macro variable in domain iterators

Re: [PATCH] irqdomain: protect macro variable in domain iterators

[Dave Martin]

On Fri, Dec 02, 2011 at 02:53:17PM +0100, Nicolas Ferre wrote:
> Signed-off-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> ---
> Error found while using those iterators in an irq controller
> initialization function.
> 
> May also need protection around irq and hwirq macro variables
> but those values are usually plain "int" anyway... Tell me if you
> feel that it should be done.
> 
>  include/linux/irqdomain.h |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 99834e58..a553004 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -82,12 +82,12 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
>  }
>  
>  #define irq_domain_for_each_hwirq(d, hw) \
> -	for (hw = d->hwirq_base; hw < d->hwirq_base + d->nr_irq; hw++)
> +	for (hw = (d)->hwirq_base; hw < (d)->hwirq_base + (d)->nr_irq; hw++)
>  
>  #define irq_domain_for_each_irq(d, hw, irq) \
> -	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
> -	     hw < d->hwirq_base + d->nr_irq; \
> -	     hw++, irq = irq_domain_to_irq(d, hw))
> +	for (hw = (d)->hwirq_base, irq = irq_domain_to_irq((d), hw); \
> +	     hw < (d)->hwirq_base + (d)->nr_irq; \
> +	     hw++, irq = irq_domain_to_irq((d), hw))

I suggest just putting all the brackets in -- if having spotted this
problem you only half-fix the macros, an opportunity is being missed;
someone have to come and fix it again later:


#define irq_domain_for_each_hwirq(d, hw) \
	for ((hw) = (d)->hwirq_base; (hw) < (d)->hwirq_base + (d)->nr_irq; (hw)++)

#define irq_domain_for_each_irq(d, hw, irq) \
	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq(d, hw); \
	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
	     (hw)++, (irq) = irq_domain_to_irq(d, hw))


If you feel happier though, you can harmlessly add the extra brackets round
the arguments to irq_domain_to_irq(), without changing the behaviour.
Arguably the "always add brackets" rule is simpler to understand.

In fact, where a macro argument is not part of a larger expression, or is an
operand to a comma-expression, there's no need for extra brackets -- all
possible operators parse at higher priority than commas.  A macro argument
which itself is a comma-expression whould have to be explicitly bracketed
in the macro invocation anyway, so there is no extra risk of the macro
expansion being parsed in an unexpected way in that case.

Cheers
---Dave

Re: [PATCH] irqdomain: protect macro variable in domain iterators

[Nicolas Ferre]

On 12/02/2011 01:59 PM, Dave Martin :
> On Fri, Dec 02, 2011 at 02:53:17PM +0100, Nicolas Ferre wrote:
>> Signed-off-by: Nicolas Ferre<nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
>> ---
>> Error found while using those iterators in an irq controller
>> initialization function.
>>
>> May also need protection around irq and hwirq macro variables
>> but those values are usually plain "int" anyway... Tell me if you
>> feel that it should be done.
>>
>>   include/linux/irqdomain.h |    8 ++++----
>>   1 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
>> index 99834e58..a553004 100644
>> --- a/include/linux/irqdomain.h
>> +++ b/include/linux/irqdomain.h
>> @@ -82,12 +82,12 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
>>   }
>>
>>   #define irq_domain_for_each_hwirq(d, hw) \
>> -	for (hw = d->hwirq_base; hw<  d->hwirq_base + d->nr_irq; hw++)
>> +	for (hw = (d)->hwirq_base; hw<  (d)->hwirq_base + (d)->nr_irq; hw++)
>>
>>   #define irq_domain_for_each_irq(d, hw, irq) \
>> -	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
>> -	     hw<  d->hwirq_base + d->nr_irq; \
>> -	     hw++, irq = irq_domain_to_irq(d, hw))
>> +	for (hw = (d)->hwirq_base, irq = irq_domain_to_irq((d), hw); \
>> +	     hw<  (d)->hwirq_base + (d)->nr_irq; \
>> +	     hw++, irq = irq_domain_to_irq((d), hw))
>
> I suggest just putting all the brackets in -- if having spotted this
> problem you only half-fix the macros, an opportunity is being missed;
> someone have to come and fix it again later:

Exactly, this is why I added a little comment to the patch:

"May also need protection around irq and hwirq macro variables
but those values are usually plain "int" anyway... Tell me if you
feel that it should be done."

> #define irq_domain_for_each_hwirq(d, hw) \
> 	for ((hw) = (d)->hwirq_base; (hw)<  (d)->hwirq_base + (d)->nr_irq; (hw)++)
>
> #define irq_domain_for_each_irq(d, hw, irq) \
> 	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq(d, hw); \
> 	     (hw)<  (d)->hwirq_base + (d)->nr_irq; \
> 	     (hw)++, (irq) = irq_domain_to_irq(d, hw))
>
>
> If you feel happier though, you can harmlessly add the extra brackets round
> the arguments to irq_domain_to_irq(), without changing the behaviour.
> Arguably the "always add brackets" rule is simpler to understand.
>
> In fact, where a macro argument is not part of a larger expression, or is an
> operand to a comma-expression, there's no need for extra brackets -- all
> possible operators parse at higher priority than commas.  A macro argument
> which itself is a comma-expression whould have to be explicitly bracketed
> in the macro invocation anyway, so there is no extra risk of the macro
> expansion being parsed in an unexpected way in that case.

Thanks for the detailed explanation. I resend the patch with the "always 
add brackets" corrections.

Best regards,
-- 
Nicolas Ferre

[PATCH v2] irqdomain: protect macro variable in domain iterators

[Nicolas Ferre]

Signed-off-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
---
v2: add brackets to each macro variable.

 include/linux/irqdomain.h |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index bd4272b..e535063 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -82,12 +82,14 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
 }
 
 #define irq_domain_for_each_hwirq(d, hw) \
-	for (hw = d->hwirq_base; hw < d->hwirq_base + d->nr_irq; hw++)
+	for ((hw) = (d)->hwirq_base; \
+	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
+	     (hw)++)
 
 #define irq_domain_for_each_irq(d, hw, irq) \
-	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
-	     hw < d->hwirq_base + d->nr_irq; \
-	     hw++, irq = irq_domain_to_irq(d, hw))
+	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq((d), (hw)); \
+	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
+	     (hw)++, (irq) = irq_domain_to_irq((d), (hw)))
 
 extern void irq_domain_add(struct irq_domain *domain);
 extern void irq_domain_del(struct irq_domain *domain);
-- 
1.7.5.4

Re: [PATCH v2] irqdomain: protect macro variable in domain iterators

[Dave Martin]

On Fri, Dec 02, 2011 at 02:30:09PM +0100, Nicolas Ferre wrote:
> Signed-off-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>

Looks OK to me:

Acked-by: Dave Martin <dave.martin-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

> ---
> v2: add brackets to each macro variable.
> 
>  include/linux/irqdomain.h |   10 ++++++----
>  1 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index bd4272b..e535063 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -82,12 +82,14 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
>  }
>  
>  #define irq_domain_for_each_hwirq(d, hw) \
> -	for (hw = d->hwirq_base; hw < d->hwirq_base + d->nr_irq; hw++)
> +	for ((hw) = (d)->hwirq_base; \
> +	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
> +	     (hw)++)
>  
>  #define irq_domain_for_each_irq(d, hw, irq) \
> -	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
> -	     hw < d->hwirq_base + d->nr_irq; \
> -	     hw++, irq = irq_domain_to_irq(d, hw))
> +	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq((d), (hw)); \
> +	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
> +	     (hw)++, (irq) = irq_domain_to_irq((d), (hw)))
>  
>  extern void irq_domain_add(struct irq_domain *domain);
>  extern void irq_domain_del(struct irq_domain *domain);
> -- 
> 1.7.5.4
> 

Re: [PATCH] irqdomain: protect macro variable in domain iterators

[Rob Herring]

On 12/02/2011 06:59 AM, Dave Martin wrote:
> On Fri, Dec 02, 2011 at 02:53:17PM +0100, Nicolas Ferre wrote:
>> Signed-off-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
>> ---
>> Error found while using those iterators in an irq controller
>> initialization function.
>>
>> May also need protection around irq and hwirq macro variables
>> but those values are usually plain "int" anyway... Tell me if you
>> feel that it should be done.
>>
>>  include/linux/irqdomain.h |    8 ++++----
>>  1 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
>> index 99834e58..a553004 100644
>> --- a/include/linux/irqdomain.h
>> +++ b/include/linux/irqdomain.h
>> @@ -82,12 +82,12 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
>>  }
>>  
>>  #define irq_domain_for_each_hwirq(d, hw) \
>> -	for (hw = d->hwirq_base; hw < d->hwirq_base + d->nr_irq; hw++)
>> +	for (hw = (d)->hwirq_base; hw < (d)->hwirq_base + (d)->nr_irq; hw++)
>>  
>>  #define irq_domain_for_each_irq(d, hw, irq) \
>> -	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
>> -	     hw < d->hwirq_base + d->nr_irq; \
>> -	     hw++, irq = irq_domain_to_irq(d, hw))
>> +	for (hw = (d)->hwirq_base, irq = irq_domain_to_irq((d), hw); \
>> +	     hw < (d)->hwirq_base + (d)->nr_irq; \
>> +	     hw++, irq = irq_domain_to_irq((d), hw))
> 
> I suggest just putting all the brackets in -- if having spotted this
> problem you only half-fix the macros, an opportunity is being missed;
> someone have to come and fix it again later:
> 
> 
> #define irq_domain_for_each_hwirq(d, hw) \
> 	for ((hw) = (d)->hwirq_base; (hw) < (d)->hwirq_base + (d)->nr_irq; (hw)++)
> 
> #define irq_domain_for_each_irq(d, hw, irq) \
> 	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq(d, hw); \
> 	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
> 	     (hw)++, (irq) = irq_domain_to_irq(d, hw))
> 

Parameters on the left side of an '=' can't be a complex expression.
Look at other iterator macros.

Rob

> 
> If you feel happier though, you can harmlessly add the extra brackets round
> the arguments to irq_domain_to_irq(), without changing the behaviour.
> Arguably the "always add brackets" rule is simpler to understand.
> 
> In fact, where a macro argument is not part of a larger expression, or is an
> operand to a comma-expression, there's no need for extra brackets -- all
> possible operators parse at higher priority than commas.  A macro argument
> which itself is a comma-expression whould have to be explicitly bracketed
> in the macro invocation anyway, so there is no extra risk of the macro
> expansion being parsed in an unexpected way in that case.
> 
> Cheers
> ---Dave

[PATCH] irqdomain: protect macro variable in domain iterators

[Nicolas Ferre]

Signed-off-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
---
Error found while using those iterators in an irq controller
initialization function.

May also need protection around irq and hwirq macro variables
but those values are usually plain "int" anyway... Tell me if you
feel that it should be done.

 include/linux/irqdomain.h |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 99834e58..a553004 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -82,12 +82,12 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
 }
 
 #define irq_domain_for_each_hwirq(d, hw) \
-	for (hw = d->hwirq_base; hw < d->hwirq_base + d->nr_irq; hw++)
+	for (hw = (d)->hwirq_base; hw < (d)->hwirq_base + (d)->nr_irq; hw++)
 
 #define irq_domain_for_each_irq(d, hw, irq) \
-	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
-	     hw < d->hwirq_base + d->nr_irq; \
-	     hw++, irq = irq_domain_to_irq(d, hw))
+	for (hw = (d)->hwirq_base, irq = irq_domain_to_irq((d), hw); \
+	     hw < (d)->hwirq_base + (d)->nr_irq; \
+	     hw++, irq = irq_domain_to_irq((d), hw))
 
 extern void irq_domain_add(struct irq_domain *domain);
 extern void irq_domain_del(struct irq_domain *domain);
-- 
1.7.5.4

Re: [PATCH] irqdomain: protect macro variable in domain iterators

[Dave Martin]

On Fri, Dec 02, 2011 at 07:51:58AM -0600, Rob Herring wrote:
> On 12/02/2011 06:59 AM, Dave Martin wrote:
> > On Fri, Dec 02, 2011 at 02:53:17PM +0100, Nicolas Ferre wrote:
> >> Signed-off-by: Nicolas Ferre <nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> >> ---
> >> Error found while using those iterators in an irq controller
> >> initialization function.
> >>
> >> May also need protection around irq and hwirq macro variables
> >> but those values are usually plain "int" anyway... Tell me if you
> >> feel that it should be done.
> >>
> >>  include/linux/irqdomain.h |    8 ++++----
> >>  1 files changed, 4 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> >> index 99834e58..a553004 100644
> >> --- a/include/linux/irqdomain.h
> >> +++ b/include/linux/irqdomain.h
> >> @@ -82,12 +82,12 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
> >>  }
> >>  
> >>  #define irq_domain_for_each_hwirq(d, hw) \
> >> -	for (hw = d->hwirq_base; hw < d->hwirq_base + d->nr_irq; hw++)
> >> +	for (hw = (d)->hwirq_base; hw < (d)->hwirq_base + (d)->nr_irq; hw++)
> >>  
> >>  #define irq_domain_for_each_irq(d, hw, irq) \
> >> -	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
> >> -	     hw < d->hwirq_base + d->nr_irq; \
> >> -	     hw++, irq = irq_domain_to_irq(d, hw))
> >> +	for (hw = (d)->hwirq_base, irq = irq_domain_to_irq((d), hw); \
> >> +	     hw < (d)->hwirq_base + (d)->nr_irq; \
> >> +	     hw++, irq = irq_domain_to_irq((d), hw))
> > 
> > I suggest just putting all the brackets in -- if having spotted this
> > problem you only half-fix the macros, an opportunity is being missed;
> > someone have to come and fix it again later:
> > 
> > 
> > #define irq_domain_for_each_hwirq(d, hw) \
> > 	for ((hw) = (d)->hwirq_base; (hw) < (d)->hwirq_base + (d)->nr_irq; (hw)++)
> > 
> > #define irq_domain_for_each_irq(d, hw, irq) \
> > 	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq(d, hw); \
> > 	     (hw) < (d)->hwirq_base + (d)->nr_irq; \
> > 	     (hw)++, (irq) = irq_domain_to_irq(d, hw))
> > 
> 
> Parameters on the left side of an '=' can't be a complex expression.
> Look at other iterator macros.

Do you mean "can't" or "shouldn't, by policy"?  I don't see a statement of
the policy, but feel free to point me at it if it exists.

An arbitrarily complex expression can appear on the left size of a C
assignment, providing that it is an lvalue of an appropriate type; though
if it involves things like casts or ?: we would rapidly get into ill-
advised obfuscated code territory.


The most plausible use I can think of it something like:

int do_something(type *result, args)
{
	widget w;
	/* ... */

	widget_for_each_whatever(*result, w) {
		/* do stuff */
	}

	/* ... */
}

I don't comment on whether this is a good idea, but from the language
point of view it is perfectly reasonable.

(Note that *result = something parses how we want, but *result++, if
generated in the macro expansion, will not)


You're right that this won't work with at least some of the existing
macros, but my view is if that if a macro can be made trivially correct,
without pitfalls, that you should do it.  As a general principle, this
helps to avoid latent bugs in the code.  I don't think we should have
a special-case rule because this is a certain special flavour of macro,
unless implementing the macro robustly becomes impossible.


Just my opinion, though -- if people want it the other way, then I don't
have a serious problem with that.

Cheers
---Dave

Re: [PATCH v2] irqdomain: protect macro variable in domain iterators

[Nicolas Ferre]

On 12/02/2011 02:44 PM, Dave Martin :
> On Fri, Dec 02, 2011 at 02:30:09PM +0100, Nicolas Ferre wrote:
>> Signed-off-by: Nicolas Ferre<nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
>
> Looks OK to me:
>
> Acked-by: Dave Martin<dave.martin-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Rob,

Do you want a different implementation for this. I think it is the 
simplest way to write this macro...

If it is ok for you, it will be interesting to include this patch 
quickly so that I will be able to queue my own patches on top of it.
(Cc: stable can be a good idea also).

Best regards,

>> ---
>> v2: add brackets to each macro variable.
>>
>>   include/linux/irqdomain.h |   10 ++++++----
>>   1 files changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
>> index bd4272b..e535063 100644
>> --- a/include/linux/irqdomain.h
>> +++ b/include/linux/irqdomain.h
>> @@ -82,12 +82,14 @@ static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
>>   }
>>
>>   #define irq_domain_for_each_hwirq(d, hw) \
>> -	for (hw = d->hwirq_base; hw<  d->hwirq_base + d->nr_irq; hw++)
>> +	for ((hw) = (d)->hwirq_base; \
>> +	     (hw)<  (d)->hwirq_base + (d)->nr_irq; \
>> +	     (hw)++)
>>
>>   #define irq_domain_for_each_irq(d, hw, irq) \
>> -	for (hw = d->hwirq_base, irq = irq_domain_to_irq(d, hw); \
>> -	     hw<  d->hwirq_base + d->nr_irq; \
>> -	     hw++, irq = irq_domain_to_irq(d, hw))
>> +	for ((hw) = (d)->hwirq_base, (irq) = irq_domain_to_irq((d), (hw)); \
>> +	     (hw)<  (d)->hwirq_base + (d)->nr_irq; \
>> +	     (hw)++, (irq) = irq_domain_to_irq((d), (hw)))
>>
>>   extern void irq_domain_add(struct irq_domain *domain);
>>   extern void irq_domain_del(struct irq_domain *domain);
>> --
>> 1.7.5.4
>>
>


-- 
Nicolas Ferre

Re: [PATCH v2] irqdomain: protect macro variable in domain iterators

[Rob Herring]

On 12/08/2011 03:37 AM, Nicolas Ferre wrote:
> On 12/02/2011 02:44 PM, Dave Martin :
>> On Fri, Dec 02, 2011 at 02:30:09PM +0100, Nicolas Ferre wrote:
>>> Signed-off-by: Nicolas Ferre<nicolas.ferre@atmel.com>
>>
>> Looks OK to me:
>>
>> Acked-by: Dave Martin<dave.martin@linaro.org>
> 
> Rob,
> 
> Do you want a different implementation for this. I think it is the
> simplest way to write this macro...
> 
> If it is ok for you, it will be interesting to include this patch
> quickly so that I will be able to queue my own patches on top of it.
> (Cc: stable can be a good idea also).
> 

Yes, it's fine. The irqdomain patches need to be taken by tglx or acked
by him. I don't think this is needed for stable. The existing users are
fine and new ones aren't going to be added to stable kernels.

Rob