Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
On 11/12/2012 10:23 AM, Russell King - ARM Linux wrote:
> On Mon, Nov 12, 2012 at 04:12:29PM +0100, Maarten Lankhorst wrote:
>> Op 08-11-12 21:23, Sasha Levin schreef:
>>> @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int
>>> combiner_nr, unsigned int i
>>> else
>>> max_nr = EXYNOS4_MAX_COMBINER_NR;
>>>
>>> - if (combiner_nr >= max_nr)
>>> - BUG();
>>> - if (irq_set_handler_data(irq, _data[combiner_nr]) != 0)
>>> - BUG();
>>> + BUG_ON(combiner_nr >= max_nr);
>>> + BUG_ON(irq_set_handler_data(irq, _data[combiner_nr]) != 0);
>>
>> Is it really a good idea to put functions that perform work in a BUG_ON?
>> I don't know, but for some reason it just feels wrong. I'd expect code to
>> compile fine if BUG_ON was a noop, so doing verification calls only, not
>> actual work..
>
> Well, it is currently defined as:
>
> include/asm-generic/bug.h:#define BUG_ON(condition) do { if
> (unlikely(condition)) BUG(); } while(0)
> include/asm-generic/bug.h:#define BUG_ON(condition) do { if (condition) ; }
> while(0)
>
> but as these can be overridden, I don't think relying on those
> implementations is a good idea; to do so would be fragile. Eg, what if
> the BUG_ON() implementation becomes just:
>
> #define BUG_ON(x)
>
> then the function call itself vanishes. So, only put the actual bug test
> inside a BUG_ON(), not the functional part which must always be executed.
Even if we ignore that modifying the side-effects is wrong, there's already
more than enough code in the kernel (both in kernel/ / mm/, and in arch/) to
cause breakage if for some reason the expression is not evaluated.
If some arch decides to not evaluate the expression there it's going to be
inherently broken.
Thanks,
Sasha
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Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
On 11/12/2012 10:12 AM, Maarten Lankhorst wrote: > Op 08-11-12 21:23, Sasha Levin schreef: >> Just use BUG_ON() instead of constructions such as: >> >> if (...) >> BUG() >> >> A simplified version of the semantic patch that makes this transformation >> is as follows: (http://coccinelle.lip6.fr/) >> >> // >> @@ >> expression e; >> @@ >> - if (e) BUG(); >> + BUG_ON(e); >> // >> >> Signed-off-by: Sasha Levin >> --- >> arch/arm/mach-exynos/common.c |6 ++ >> 1 file changed, 2 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c >> index 4e577f6..6a55a5a 100644 >> --- a/arch/arm/mach-exynos/common.c >> +++ b/arch/arm/mach-exynos/common.c >> @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int >> combiner_nr, unsigned int i >> else >> max_nr = EXYNOS4_MAX_COMBINER_NR; >> >> -if (combiner_nr >= max_nr) >> -BUG(); >> -if (irq_set_handler_data(irq, _data[combiner_nr]) != 0) >> -BUG(); >> +BUG_ON(combiner_nr >= max_nr); >> +BUG_ON(irq_set_handler_data(irq, _data[combiner_nr]) != 0); > Is it really a good idea to put functions that perform work in a BUG_ON? > I don't know, but for some reason it just feels wrong. I'd expect code to > compile fine if BUG_ON was a noop, so doing verification calls only, not > actual work.. You can't modify the side-effects of a macro based on kernel configuration. If we're evaluating the expression when BUG_ON() is enabled, you must also evaluate the expression when BUG_ON() is not enabled (HAVE_ARCH_BUG_ON is not set). The only reason I'd not include function calls in a BUG_ON() call is due to readability considerations. In this case it looked okay to me, but if someone thinks that getting the function call into the BUG_ON() complicated things I'm fine with skipping that. Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
On Mon, Nov 12, 2012 at 04:12:29PM +0100, Maarten Lankhorst wrote:
> Op 08-11-12 21:23, Sasha Levin schreef:
> > @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int
> > combiner_nr, unsigned int i
> > else
> > max_nr = EXYNOS4_MAX_COMBINER_NR;
> >
> > - if (combiner_nr >= max_nr)
> > - BUG();
> > - if (irq_set_handler_data(irq, _data[combiner_nr]) != 0)
> > - BUG();
> > + BUG_ON(combiner_nr >= max_nr);
> > + BUG_ON(irq_set_handler_data(irq, _data[combiner_nr]) != 0);
>
> Is it really a good idea to put functions that perform work in a BUG_ON?
> I don't know, but for some reason it just feels wrong. I'd expect code to
> compile fine if BUG_ON was a noop, so doing verification calls only, not
> actual work..
Well, it is currently defined as:
include/asm-generic/bug.h:#define BUG_ON(condition) do { if
(unlikely(condition)) BUG(); } while(0)
include/asm-generic/bug.h:#define BUG_ON(condition) do { if (condition) ; }
while(0)
but as these can be overridden, I don't think relying on those
implementations is a good idea; to do so would be fragile. Eg, what if
the BUG_ON() implementation becomes just:
#define BUG_ON(x)
then the function call itself vanishes. So, only put the actual bug test
inside a BUG_ON(), not the functional part which must always be executed.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
Op 08-11-12 21:23, Sasha Levin schreef: > Just use BUG_ON() instead of constructions such as: > > if (...) > BUG() > > A simplified version of the semantic patch that makes this transformation > is as follows: (http://coccinelle.lip6.fr/) > > // > @@ > expression e; > @@ > - if (e) BUG(); > + BUG_ON(e); > // > > Signed-off-by: Sasha Levin > --- > arch/arm/mach-exynos/common.c |6 ++ > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c > index 4e577f6..6a55a5a 100644 > --- a/arch/arm/mach-exynos/common.c > +++ b/arch/arm/mach-exynos/common.c > @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int > combiner_nr, unsigned int i > else > max_nr = EXYNOS4_MAX_COMBINER_NR; > > - if (combiner_nr >= max_nr) > - BUG(); > - if (irq_set_handler_data(irq, _data[combiner_nr]) != 0) > - BUG(); > + BUG_ON(combiner_nr >= max_nr); > + BUG_ON(irq_set_handler_data(irq, _data[combiner_nr]) != 0); Is it really a good idea to put functions that perform work in a BUG_ON? I don't know, but for some reason it just feels wrong. I'd expect code to compile fine if BUG_ON was a noop, so doing verification calls only, not actual work.. ~Maarten -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
Op 08-11-12 21:23, Sasha Levin schreef: Just use BUG_ON() instead of constructions such as: if (...) BUG() A simplified version of the semantic patch that makes this transformation is as follows: (http://coccinelle.lip6.fr/) // smpl @@ expression e; @@ - if (e) BUG(); + BUG_ON(e); // /smpl Signed-off-by: Sasha Levin sasha.le...@oracle.com --- arch/arm/mach-exynos/common.c |6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c index 4e577f6..6a55a5a 100644 --- a/arch/arm/mach-exynos/common.c +++ b/arch/arm/mach-exynos/common.c @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int combiner_nr, unsigned int i else max_nr = EXYNOS4_MAX_COMBINER_NR; - if (combiner_nr = max_nr) - BUG(); - if (irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0) - BUG(); + BUG_ON(combiner_nr = max_nr); + BUG_ON(irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0); Is it really a good idea to put functions that perform work in a BUG_ON? I don't know, but for some reason it just feels wrong. I'd expect code to compile fine if BUG_ON was a noop, so doing verification calls only, not actual work.. ~Maarten -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
On Mon, Nov 12, 2012 at 04:12:29PM +0100, Maarten Lankhorst wrote:
Op 08-11-12 21:23, Sasha Levin schreef:
@@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int
combiner_nr, unsigned int i
else
max_nr = EXYNOS4_MAX_COMBINER_NR;
- if (combiner_nr = max_nr)
- BUG();
- if (irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0)
- BUG();
+ BUG_ON(combiner_nr = max_nr);
+ BUG_ON(irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0);
Is it really a good idea to put functions that perform work in a BUG_ON?
I don't know, but for some reason it just feels wrong. I'd expect code to
compile fine if BUG_ON was a noop, so doing verification calls only, not
actual work..
Well, it is currently defined as:
include/asm-generic/bug.h:#define BUG_ON(condition) do { if
(unlikely(condition)) BUG(); } while(0)
include/asm-generic/bug.h:#define BUG_ON(condition) do { if (condition) ; }
while(0)
but as these can be overridden, I don't think relying on those
implementations is a good idea; to do so would be fragile. Eg, what if
the BUG_ON() implementation becomes just:
#define BUG_ON(x)
then the function call itself vanishes. So, only put the actual bug test
inside a BUG_ON(), not the functional part which must always be executed.
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
On 11/12/2012 10:12 AM, Maarten Lankhorst wrote: Op 08-11-12 21:23, Sasha Levin schreef: Just use BUG_ON() instead of constructions such as: if (...) BUG() A simplified version of the semantic patch that makes this transformation is as follows: (http://coccinelle.lip6.fr/) // smpl @@ expression e; @@ - if (e) BUG(); + BUG_ON(e); // /smpl Signed-off-by: Sasha Levin sasha.le...@oracle.com --- arch/arm/mach-exynos/common.c |6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c index 4e577f6..6a55a5a 100644 --- a/arch/arm/mach-exynos/common.c +++ b/arch/arm/mach-exynos/common.c @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int combiner_nr, unsigned int i else max_nr = EXYNOS4_MAX_COMBINER_NR; -if (combiner_nr = max_nr) -BUG(); -if (irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0) -BUG(); +BUG_ON(combiner_nr = max_nr); +BUG_ON(irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0); Is it really a good idea to put functions that perform work in a BUG_ON? I don't know, but for some reason it just feels wrong. I'd expect code to compile fine if BUG_ON was a noop, so doing verification calls only, not actual work.. You can't modify the side-effects of a macro based on kernel configuration. If we're evaluating the expression when BUG_ON() is enabled, you must also evaluate the expression when BUG_ON() is not enabled (HAVE_ARCH_BUG_ON is not set). The only reason I'd not include function calls in a BUG_ON() call is due to readability considerations. In this case it looked okay to me, but if someone thinks that getting the function call into the BUG_ON() complicated things I'm fine with skipping that. Thanks, Sasha -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] ARM: EXYNOS: use BUG_ON where possible
On 11/12/2012 10:23 AM, Russell King - ARM Linux wrote:
On Mon, Nov 12, 2012 at 04:12:29PM +0100, Maarten Lankhorst wrote:
Op 08-11-12 21:23, Sasha Levin schreef:
@@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int
combiner_nr, unsigned int i
else
max_nr = EXYNOS4_MAX_COMBINER_NR;
- if (combiner_nr = max_nr)
- BUG();
- if (irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0)
- BUG();
+ BUG_ON(combiner_nr = max_nr);
+ BUG_ON(irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0);
Is it really a good idea to put functions that perform work in a BUG_ON?
I don't know, but for some reason it just feels wrong. I'd expect code to
compile fine if BUG_ON was a noop, so doing verification calls only, not
actual work..
Well, it is currently defined as:
include/asm-generic/bug.h:#define BUG_ON(condition) do { if
(unlikely(condition)) BUG(); } while(0)
include/asm-generic/bug.h:#define BUG_ON(condition) do { if (condition) ; }
while(0)
but as these can be overridden, I don't think relying on those
implementations is a good idea; to do so would be fragile. Eg, what if
the BUG_ON() implementation becomes just:
#define BUG_ON(x)
then the function call itself vanishes. So, only put the actual bug test
inside a BUG_ON(), not the functional part which must always be executed.
Even if we ignore that modifying the side-effects is wrong, there's already
more than enough code in the kernel (both in kernel/ / mm/, and in arch/) to
cause breakage if for some reason the expression is not evaluated.
If some arch decides to not evaluate the expression there it's going to be
inherently broken.
Thanks,
Sasha
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] ARM: EXYNOS: use BUG_ON where possible
Just use BUG_ON() instead of constructions such as: if (...) BUG() A simplified version of the semantic patch that makes this transformation is as follows: (http://coccinelle.lip6.fr/) // @@ expression e; @@ - if (e) BUG(); + BUG_ON(e); // Signed-off-by: Sasha Levin --- arch/arm/mach-exynos/common.c |6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c index 4e577f6..6a55a5a 100644 --- a/arch/arm/mach-exynos/common.c +++ b/arch/arm/mach-exynos/common.c @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int combiner_nr, unsigned int i else max_nr = EXYNOS4_MAX_COMBINER_NR; - if (combiner_nr >= max_nr) - BUG(); - if (irq_set_handler_data(irq, _data[combiner_nr]) != 0) - BUG(); + BUG_ON(combiner_nr >= max_nr); + BUG_ON(irq_set_handler_data(irq, _data[combiner_nr]) != 0); irq_set_chained_handler(irq, combiner_handle_cascade_irq); } -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] ARM: EXYNOS: use BUG_ON where possible
Just use BUG_ON() instead of constructions such as: if (...) BUG() A simplified version of the semantic patch that makes this transformation is as follows: (http://coccinelle.lip6.fr/) // smpl @@ expression e; @@ - if (e) BUG(); + BUG_ON(e); // /smpl Signed-off-by: Sasha Levin sasha.le...@oracle.com --- arch/arm/mach-exynos/common.c |6 ++ 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c index 4e577f6..6a55a5a 100644 --- a/arch/arm/mach-exynos/common.c +++ b/arch/arm/mach-exynos/common.c @@ -465,10 +465,8 @@ static void __init combiner_cascade_irq(unsigned int combiner_nr, unsigned int i else max_nr = EXYNOS4_MAX_COMBINER_NR; - if (combiner_nr = max_nr) - BUG(); - if (irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0) - BUG(); + BUG_ON(combiner_nr = max_nr); + BUG_ON(irq_set_handler_data(irq, combiner_data[combiner_nr]) != 0); irq_set_chained_handler(irq, combiner_handle_cascade_irq); } -- 1.7.10.4 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
