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authorSteven Rostedt <rostedt@goodmis.org>2016-05-13 15:30:13 +0200
committerIngo Molnar <mingo@kernel.org>2016-05-13 16:12:53 +0200
commitef0491ea17f8019821c7e9c8e801184ecf17f85a (patch)
treeee69c01a8ed8fe7aab6106adde37bbb8a94b0aa6
parent50605ffbdaf6d7ccab70d4631fd8347fc78af14f (diff)
ARM: Hide finish_arch_post_lock_switch() from modules
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 with modular configs: 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. Arnd suggested reordering the header files, which wasn't popular, so let's use 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. Tested-by: Guenter Roeck <linux@roeck-us.net> 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> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@suse.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King - ARM Linux <linux@armlinux.org.uk> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-arm-kernel@lists.infradead.org Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler") Link: http://lkml.kernel.org/r/1463146234-161304-1-git-send-email-arnd@arndb.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/arm/include/asm/mmu_context.h2
1 files changed, 2 insertions, 0 deletions
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 */