* [RFC PATCH v2 0/9] Remove useless on_each_cpu return value
@ 2012-01-08 13:32 Gilad Ben-Yossef
2012-01-08 13:32 ` [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value Gilad Ben-Yossef
2012-01-08 13:32 ` [RFC PATCH v2 8/9] smp: refactor on_each_cpu to void returning func Gilad Ben-Yossef
0 siblings, 2 replies; 6+ messages in thread
From: Gilad Ben-Yossef @ 2012-01-08 13:32 UTC (permalink / raw)
To: linux-arm-kernel
on_each_cpu() returns as its own return value the return value of
smp_call_function(). smp_call_function() in turn returns a hard
coded value of zero.
Some callers to on_each_cpu() waste cycles and bloat code space
by checking the return value to on_each_cpu(), probably for
historical reasons.
This patch set refactors callers to not test on_each_cpu()
(fixed) return value and then refactors on_each_cpu to
return void to avoid confusing future users.
In other words, this patch aims to delete 18 source code lines
while not changing any functionality :-)
I tested as best as I could the x86 changes and compiled some
of the others, but I don't have access to all the needed hardware
for testing. Reviewers and testers welcome!
The only change from the first version is the addition of a
proper Signed-off-by line.
This patch set is also available on branch on_each_cpu_ret_v2
at git://github.com/gby/linux.git
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
CC: Michal Nazarewicz <mina86@mina86.com>
CC: David Airlie <airlied@linux.ie>
CC: dri-devel at lists.freedesktop.org
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Grant Likely <grant.likely@secretlab.ca>
CC: Rob Herring <rob.herring@calxeda.com>
CC: linuxppc-dev at lists.ozlabs.org
CC: devicetree-discuss at lists.ozlabs.org
CC: Richard Henderson <rth@twiddle.net>
CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
CC: Matt Turner <mattst88@gmail.com>
CC: linux-alpha at vger.kernel.org
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: x86 at kernel.org
CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: linux-ia64 at vger.kernel.org
CC: Will Deacon <will.deacon@arm.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
CC: Russell King <linux@arm.linux.org.uk>
CC: linux-arm-kernel at lists.infradead.org
Gilad Ben-Yossef (9):
arm: avoid using on_each_cpu hard coded ret value
ia64: avoid using on_each_cpu hard coded ret value
x86: avoid using on_each_cpu hard coded ret value
alpha: avoid using on_each_cpu hard coded ret value
ppc: avoid using on_each_cpu hard coded ret value
agp: avoid using on_each_cpu hard coded ret value
drm: avoid using on_each_cpu hard coded ret value
smp: refactor on_each_cpu to void returning func
x86: refactor wbinvd_on_all_cpus to void function
arch/alpha/kernel/smp.c | 7 ++-----
arch/arm/kernel/perf_event.c | 2 +-
arch/ia64/kernel/perfmon.c | 12 ++----------
arch/powerpc/kernel/rtas.c | 3 +--
arch/x86/include/asm/smp.h | 5 ++---
arch/x86/lib/cache-smp.c | 4 ++--
drivers/char/agp/generic.c | 3 +--
drivers/gpu/drm/drm_cache.c | 3 +--
include/linux/smp.h | 7 +++----
kernel/smp.c | 6 ++----
10 files changed, 17 insertions(+), 35 deletions(-)
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value
2012-01-08 13:32 [RFC PATCH v2 0/9] Remove useless on_each_cpu return value Gilad Ben-Yossef
@ 2012-01-08 13:32 ` Gilad Ben-Yossef
2012-01-08 16:12 ` Russell King - ARM Linux
2012-01-08 13:32 ` [RFC PATCH v2 8/9] smp: refactor on_each_cpu to void returning func Gilad Ben-Yossef
1 sibling, 1 reply; 6+ messages in thread
From: Gilad Ben-Yossef @ 2012-01-08 13:32 UTC (permalink / raw)
To: linux-arm-kernel
on_each_cpu always returns a hard coded return code of zero.
Removing all tests based on this return value saves run time
cycles for compares and code bloat for branches.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Paul Mackerras <paulus@samba.org>
CC: Ingo Molnar <mingo@elte.hu>
CC: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
CC: Russell King <linux@arm.linux.org.uk>
CC: Grant Likely <grant.likely@secretlab.ca>
CC: Rob Herring <rob.herring@calxeda.com>
CC: linux-arm-kernel at lists.infradead.org
CC: devicetree-discuss at lists.ozlabs.org
---
arch/arm/kernel/perf_event.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 5bb91bf..6e9acb7 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -616,7 +616,7 @@ static int __init
cpu_pmu_reset(void)
{
if (cpu_pmu && cpu_pmu->reset)
- return on_each_cpu(cpu_pmu->reset, NULL, 1);
+ on_each_cpu(cpu_pmu->reset, NULL, 1);
return 0;
}
arch_initcall(cpu_pmu_reset);
--
1.7.0.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [RFC PATCH v2 8/9] smp: refactor on_each_cpu to void returning func
2012-01-08 13:32 [RFC PATCH v2 0/9] Remove useless on_each_cpu return value Gilad Ben-Yossef
2012-01-08 13:32 ` [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value Gilad Ben-Yossef
@ 2012-01-08 13:32 ` Gilad Ben-Yossef
2012-01-08 16:14 ` Russell King - ARM Linux
1 sibling, 1 reply; 6+ messages in thread
From: Gilad Ben-Yossef @ 2012-01-08 13:32 UTC (permalink / raw)
To: linux-arm-kernel
on_each_cpu returns the retunr value of smp_call_function
which is hard coded to 0.
Refactor on_each_cpu to a void function and the few callers
that check the return value to save compares and branches.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
CC: David Airlie <airlied@linux.ie>
CC: dri-devel at lists.freedesktop.org
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Grant Likely <grant.likely@secretlab.ca>
CC: Rob Herring <rob.herring@calxeda.com>
CC: linuxppc-dev at lists.ozlabs.org
CC: devicetree-discuss at lists.ozlabs.org
CC: Richard Henderson <rth@twiddle.net>
CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
CC: Matt Turner <mattst88@gmail.com>
CC: linux-alpha at vger.kernel.org
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: x86 at kernel.org
CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: linux-ia64 at vger.kernel.org
CC: Will Deacon <will.deacon@arm.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
CC: Russell King <linux@arm.linux.org.uk>
CC: linux-arm-kernel at lists.infradead.org
---
include/linux/smp.h | 7 +++----
kernel/smp.c | 6 ++----
2 files changed, 5 insertions(+), 8 deletions(-)
diff --git a/include/linux/smp.h b/include/linux/smp.h
index 8cc38d3..050ddd4 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -99,7 +99,7 @@ static inline void call_function_init(void) { }
/*
* Call a function on all processors
*/
-int on_each_cpu(smp_call_func_t func, void *info, int wait);
+void on_each_cpu(smp_call_func_t func, void *info, int wait);
/*
* Mark the boot cpu "online" so that it can call console drivers in
@@ -126,12 +126,11 @@ static inline int up_smp_call_function(smp_call_func_t func, void *info)
#define smp_call_function(func, info, wait) \
(up_smp_call_function(func, info))
#define on_each_cpu(func,info,wait) \
- ({ \
+ { \
local_irq_disable(); \
func(info); \
local_irq_enable(); \
- 0; \
- })
+ }
static inline void smp_send_reschedule(int cpu) { }
#define num_booting_cpus() 1
#define smp_prepare_boot_cpu() do {} while (0)
diff --git a/kernel/smp.c b/kernel/smp.c
index db197d6..f66a1b2 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -687,17 +687,15 @@ void __init smp_init(void)
* early_boot_irqs_disabled is set. Use local_irq_save/restore() instead
* of local_irq_disable/enable().
*/
-int on_each_cpu(void (*func) (void *info), void *info, int wait)
+void on_each_cpu(void (*func) (void *info), void *info, int wait)
{
unsigned long flags;
- int ret = 0;
preempt_disable();
- ret = smp_call_function(func, info, wait);
+ smp_call_function(func, info, wait);
local_irq_save(flags);
func(info);
local_irq_restore(flags);
preempt_enable();
- return ret;
}
EXPORT_SYMBOL(on_each_cpu);
--
1.7.0.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value
2012-01-08 13:32 ` [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value Gilad Ben-Yossef
@ 2012-01-08 16:12 ` Russell King - ARM Linux
2012-01-08 16:25 ` Gilad Ben-Yossef
0 siblings, 1 reply; 6+ messages in thread
From: Russell King - ARM Linux @ 2012-01-08 16:12 UTC (permalink / raw)
To: linux-arm-kernel
On Sun, Jan 08, 2012 at 03:32:21PM +0200, Gilad Ben-Yossef wrote:
> on_each_cpu always returns a hard coded return code of zero.
>
> Removing all tests based on this return value saves run time
> cycles for compares and code bloat for branches.
>
> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
> CC: Will Deacon <will.deacon@arm.com>
> CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Ingo Molnar <mingo@elte.hu>
> CC: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
> CC: Russell King <linux@arm.linux.org.uk>
Reviewed-by: Russell King <rmk+kernel@arm.linux.org.uk>
> CC: Grant Likely <grant.likely@secretlab.ca>
> CC: Rob Herring <rob.herring@calxeda.com>
> CC: linux-arm-kernel at lists.infradead.org
> CC: devicetree-discuss at lists.ozlabs.org
> ---
> arch/arm/kernel/perf_event.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index 5bb91bf..6e9acb7 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -616,7 +616,7 @@ static int __init
> cpu_pmu_reset(void)
> {
> if (cpu_pmu && cpu_pmu->reset)
> - return on_each_cpu(cpu_pmu->reset, NULL, 1);
> + on_each_cpu(cpu_pmu->reset, NULL, 1);
There's not much to review here...
Thanks.
> return 0;
> }
> arch_initcall(cpu_pmu_reset);
> --
> 1.7.0.4
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC PATCH v2 8/9] smp: refactor on_each_cpu to void returning func
2012-01-08 13:32 ` [RFC PATCH v2 8/9] smp: refactor on_each_cpu to void returning func Gilad Ben-Yossef
@ 2012-01-08 16:14 ` Russell King - ARM Linux
0 siblings, 0 replies; 6+ messages in thread
From: Russell King - ARM Linux @ 2012-01-08 16:14 UTC (permalink / raw)
To: linux-arm-kernel
On Sun, Jan 08, 2012 at 03:32:28PM +0200, Gilad Ben-Yossef wrote:
> on_each_cpu returns the retunr value of smp_call_function
> which is hard coded to 0.
>
> Refactor on_each_cpu to a void function and the few callers
> that check the return value to save compares and branches.
>
> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
> CC: David Airlie <airlied@linux.ie>
> CC: dri-devel at lists.freedesktop.org
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Grant Likely <grant.likely@secretlab.ca>
> CC: Rob Herring <rob.herring@calxeda.com>
> CC: linuxppc-dev at lists.ozlabs.org
> CC: devicetree-discuss at lists.ozlabs.org
> CC: Richard Henderson <rth@twiddle.net>
> CC: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
> CC: Matt Turner <mattst88@gmail.com>
> CC: linux-alpha at vger.kernel.org
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: x86 at kernel.org
> CC: Tony Luck <tony.luck@intel.com>
> CC: Fenghua Yu <fenghua.yu@intel.com>
> CC: linux-ia64 at vger.kernel.org
> CC: Will Deacon <will.deacon@arm.com>
> CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
> CC: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
> CC: Russell King <linux@arm.linux.org.uk>
As there's only one place in the ARM code where we look at the return
value, and you've patched that away in patch 1, this looks fine. I've
not checked for users outside of arch/arm, so:
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value
2012-01-08 16:12 ` Russell King - ARM Linux
@ 2012-01-08 16:25 ` Gilad Ben-Yossef
0 siblings, 0 replies; 6+ messages in thread
From: Gilad Ben-Yossef @ 2012-01-08 16:25 UTC (permalink / raw)
To: linux-arm-kernel
On Sun, Jan 8, 2012 at 6:12 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
<SNIP>
>> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
>> index 5bb91bf..6e9acb7 100644
>> --- a/arch/arm/kernel/perf_event.c
>> +++ b/arch/arm/kernel/perf_event.c
>> @@ -616,7 +616,7 @@ static int __init
>> ?cpu_pmu_reset(void)
>> ?{
>> ? ? ? if (cpu_pmu && cpu_pmu->reset)
>> - ? ? ? ? ? ? return on_each_cpu(cpu_pmu->reset, NULL, 1);
>> + ? ? ? ? ? ? on_each_cpu(cpu_pmu->reset, NULL, 1);
>
> There's not much to review here...
Oh, I've introduced fatal bugs with less... :-)
Thanks for the review.
Gilad
--
Gilad Ben-Yossef
Chief Coffee Drinker
gilad at benyossef.com
Israel Cell: +972-52-8260388
US Cell: +1-973-8260388
http://benyossef.com
"Unfortunately, cache misses are an equal opportunity pain provider."
-- Mike Galbraith, LKML
^ permalink raw reply [flat|nested] 6+ messages in thread
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Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2012-01-08 13:32 [RFC PATCH v2 0/9] Remove useless on_each_cpu return value Gilad Ben-Yossef
2012-01-08 13:32 ` [RFC PATCH v2 1/9] arm: avoid using on_each_cpu hard coded ret value Gilad Ben-Yossef
2012-01-08 16:12 ` Russell King - ARM Linux
2012-01-08 16:25 ` Gilad Ben-Yossef
2012-01-08 13:32 ` [RFC PATCH v2 8/9] smp: refactor on_each_cpu to void returning func Gilad Ben-Yossef
2012-01-08 16:14 ` Russell King - ARM Linux
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