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Date: Fri, 27 Nov 2015 08:42:24 +0100 From: Ingo Molnar <mingo@...nel.org> To: Chris Wilson <chris@...is-wilson.co.uk> Cc: Valentin Rothberg <valentinrothberg@...il.com>, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, Patrick Plagwitz <patrick.plagwitz@....de>, Andreas Ziegler <ziegler@...fau.de>, Daniel Lohmann <dl@...fau.de> Subject: Re: kernel: stop_machine: report (un)dead code (and feedback request) * Chris Wilson <chris@...is-wilson.co.uk> wrote: > On Thu, Nov 26, 2015 at 03:45:59PM +0100, Valentin Rothberg wrote: > > Hi Chris, > > > > your commit 4c477de14237 ("kernel: remove stop_machine() Kconfig > > dependency") has shown up in today's linux-next tree (20151126). > > The commit changes the #ifdef condition in kernel/stop_machine.c > > from/to: > > > > -#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP) > > +#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU) > > > > Although this change fixes certain configs on X86, the condition now is > > a tautology since CONFIG_SMP is already required to compile the file: > > > > kernel/Makefile:65:obj-$(CONFIG_SMP) += stop_machine.o > > > > AFAIU, we can safely remove this #ifdef? > > That seems logical. The argument in favour of it would be to keep the > ifdeffery around the function defintion the same as the function > declaration in stop_machine.h. But this would introduce a bit of fragility: we could re-introduce the same regression that the commit fixes, if we ever changed the SMP dependency for stop_machine.c. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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