[RFC PATCH 0/9] Remove useless on_each_cpu return value

Gilad Ben-Yossef gilad at benyossef.com
Wed Jan 4 03:08:33 EST 2012

2012/1/3 Michal Nazarewicz <mina86 at mina86.com>:
> On Tue, 03 Jan 2012 15:19:04 +0100, Gilad Ben-Yossef <gilad at benyossef.com>
> wrote:
>> 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!
> Other then the lack of Signed-off-by in the patches, looks good to me,

Blimey! I'll resend with a proper Signed-off-by after more people have
a chance to
comment. And thanks for the review.

> even though personally I'd choose a bottom-up approach, ie. make
> smp_call_function() return void and from that conclude that
> on_each_cpu() can return void.  With those patches, we have a situation,
> where smp_call_function() has a return value which is then lost for no
> immediately apparent reason lost in on_each_cpu().

There are so many call site of smp_call_function() that do not check the
return value right now that I think we can tolerate it for just a
little bit longer
until that get fixed as well... :-)


Gilad Ben-Yossef
Chief Coffee Drinker
gilad at benyossef.com
Israel Cell: +972-52-8260388
US Cell: +1-973-8260388

"Unfortunately, cache misses are an equal opportunity pain provider."
-- Mike Galbraith, LKML

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