Messages in this thread | | | Subject | Re: [PATCH] ARM: hide finish_arch_post_lock_switch from modules | From | Guenter Roeck <> | Date | Fri, 13 May 2016 06:51:05 -0700 |
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On 05/13/2016 06:30 AM, Arnd Bergmann wrote: > From: Steven Rostedt <rostedt@goodmis.org> > > The introduction of switch_mm_irqs_off() brought back an old bug > regarding the use of preempt_enable_no_resched: > > As part of 62b94a08da1b ("sched/preempt: Take away > preempt_enable_no_resched() from modules"), the definition of > preempt_enable_no_resched() is only available in built-in code, > not in loadable modules, so we can't generally use it from header > files. However, the ARM version of finish_arch_post_lock_switch() > calls preempt_enable_no_resched() and is defined as a static > inline function in asm/mmu_context.h. This in turn means we cannot > include asm/mmu_context.h from modules. > > With today's tip tree, asm/mmu_context.h gets included from > linux/mmu_context.h, which is normally the exact pattern one would > expect, but unfortunately, linux/mmu_context.h can be included from > the vhost driver that is a loadable module, now causing this compile > time error: > > In file included from ../include/linux/mmu_context.h:4:0, > from ../drivers/vhost/vhost.c:18: > ../arch/arm/include/asm/mmu_context.h: In function 'finish_arch_post_lock_switch': > ../arch/arm/include/asm/mmu_context.h:88:3: error: implicit declaration of function 'preempt_enable_no_resched' [-Werror=implicit-function-declaration] > preempt_enable_no_resched(); > > Andy already tried to fix the bug by including linux/preempt.h > from asm/mmu_context.h, but that didn't help. I suggested reordering > the header files, which wasn't popular, but Steve came up with this > workaround instead: > > The finish_arch_post_lock_switch() definition is now also hidden > inside of #ifdef MODULE, so we don't see anything referencing > preempt_enable_no_resched() from a header file. I've built a > few hundred randconfig kernels with this, and did not see any > new problems. > > Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler") > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Guenter Roeck <linux@roeck-us.net>
> --- > arch/arm/include/asm/mmu_context.h | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h > index ed73babc0dc9..3cc14dd8587c 100644 > --- a/arch/arm/include/asm/mmu_context.h > +++ b/arch/arm/include/asm/mmu_context.h > @@ -67,6 +67,7 @@ static inline void check_and_switch_context(struct mm_struct *mm, > cpu_switch_mm(mm->pgd, mm); > } > > +#ifndef MODULE > #define finish_arch_post_lock_switch \ > finish_arch_post_lock_switch > static inline void finish_arch_post_lock_switch(void) > @@ -88,6 +89,7 @@ static inline void finish_arch_post_lock_switch(void) > preempt_enable_no_resched(); > } > } > +#endif /* !MODULE */ > > #endif /* CONFIG_MMU */ > >
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