On Mon, 31 Mar 2014 14:45:32 -0700
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, Mar 31, 2014 at 12:24 AM, Martin Schwidefsky
> <schwidefsky@xxxxxxxxxx> wrote:
> >
> > There are two memory management related changes, the CMMA support for
> > KVM to avoid swap-in of freed pages and the split page table lock for
> > the PMD level. These two come with common code changes in mm/.
>
> Ugh. I pulled it, but things like this makes me want to dig my eyes
> out with a spoon:
>
> +#ifdef finish_arch_post_lock_switch
> + finish_arch_post_lock_switch();
> +#endif
>
> when I think the proper thing to do would have been to move the
> #ifndef that creates an empty finish_arch_post_lock_switch() from
> kernel/sched/sched.h to some common file, or possibly even just
> duplicate it.
>
> I detest #ifdef's in the middle of code. Yes, we do have them, but we
> should try to avoid adding more of them.
>
> Maybe we could have a <linux/mmu_context.h> that includes the
> <asm/mmu_context.h> and then does that "let's add the dummy function
> for architectures that don't need it"?
>
> Added Ingo to the cc, since this ends up intersecting with the
> scheduler code that now does the wrapper on its own.
Yes, I feel the pain. I actually tried to move the finish_arch_post_lock_switch
to linux/mmu_context.h but it turned out that this does not work. It broke
the corgi_defconfig, this is what I got from the friendly kbuild test robot:
-- snip
tree: git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux.git features
head: 05bb2956f28ff01a102bf16702ba7bcb116ecf72
commit: 8f6d84ba48d8d4377c61477803c8ff2cd4b007b7 [10/14] sched/mm: call finish_arch_post_lock_switch in idle_task_exit and use_mm
config: make ARCH=arm corgi_defconfig
All error/warnings:
In file included from include/linux/mmu_context.h:5:0,
from drivers/usb/gadget/inode.c:27:
arch/arm/include/asm/mmu_context.h: In function 'finish_arch_post_lock_switch':
>> arch/arm/include/asm/mmu_context.h:82:3: error: implicit declaration of function 'preempt_enable_no_resched' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
vim +/preempt_enable_no_resched +82 arch/arm/include/asm/mmu_context.h
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 76 */
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 77 preempt_disable();
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 78 if (mm->context.switch_pending) {
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 79 mm->context.switch_pending = 0;
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 80 cpu_switch_mm(mm->pgd, mm);
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 81 }
bdae73cd arch/arm/include/asm/mmu_context.h Catalin Marinas 2013-07-23 @82 preempt_enable_no_resched();
b9d4d42a arch/arm/include/asm/mmu_context.h Catalin Marinas 2011-11-28 83 }
b9d4d42a arch/arm/include/asm/mmu_context.h Catalin Marinas 2011-11-28 84 }
^1da177e include/asm-arm/mmu_context.h Linus Torvalds 2005-04-16 85
:::::: The code at line 82 was first introduced by commit
:::::: bdae73cd374e28db544fdd9b77de689a36e3c129 ARM: 7790/1: Fix deferred mm switch on VIVT processors
:::::: TO: Catalin Marinas <catalin.marinas@xxxxxxx>
:::::: CC: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
-- snip
I gave up after a few hours trying to solve the header dependencies, the two
trouble makes are alpha with the task_thread_info call in mmu_context.h and
arm with the preempt_enable_no_resched call. Welcome to include file hell.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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