From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752910AbcEMNdD (ORCPT ); Fri, 13 May 2016 09:33:03 -0400 Received: from mout.kundenserver.de ([217.72.192.75]:64127 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752800AbcEMNdB (ORCPT ); Fri, 13 May 2016 09:33:01 -0400 From: Arnd Bergmann To: Ingo Molnar Cc: Andy Lutomirski , Steven Rostedt , Russell King - ARM Linux , Guenter Roeck , Ard Biesheuvel , Peter Zijlstra , Frederic Weisbecker , linux-kernel@vger.kernel.org, Andy Lutomirski , Thomas Gleixner , Borislav Petkov , Mel Gorman , linux-arm-kernel@lists.infradead.org, Arnd Bergmann Subject: [PATCH] ARM: hide finish_arch_post_lock_switch from modules Date: Fri, 13 May 2016 15:30:13 +0200 Message-Id: <1463146234-161304-1-git-send-email-arnd@arndb.de> X-Mailer: git-send-email 2.7.0 X-Provags-ID: V03:K0:9R7HH3c0V9v9CFl7F6q8/bP9LDvMLrIqe+h5L0lfDSpNBQkk9ad 0CplOtGwAUIuXZRp3KWdd0b2l4pOEbIkbEmR/bnWfNVLEr425rX7TGItLMQZYBZRtWTZ/R7 WSJ2GTjxI2xUkU1unbmxL6LmhOnAvx/KTPUg7THBVPD8tdfnyIZxASpDgdZsD3mwAKHasLJ JbNlZYxOMKZQOkAAOSFNQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:FIWZ6fI6PI4=:rD0Ryc83ZmfsGhAU4NwGYM MtgQTVCUdDBid7tArbCwWgGbFCeLIh6bQUV0B0uH368WNdD6dN9hBowA2od+YTl+vIXEct+l1 xgrD/8FN4nAPvUk9hoZ3Ah8MXcbGhdCBZqZlQ4Ld+G4DNu6AkSHOQsepr5YZeozSm+2p4EASl 7xmz04HxWa1RW3Z68UQqZkiLVXLjwT/564La9vvVg71ou7DfI1TG5GN2V4A5YJMGY3tQsNsl4 XFbxgHNDkCcb0ZjwQVNJmu0bm1Mzr6jnX2ban8vRYeQcGIQfU4NaEC8E/9V83MtY5/dPPDbWr 7UH0loNOKY7keI28Yd1m32PaMQ29arSnEO5Y4Zna+uSOOyTXx3xoK3dvTQKwfhALt9OHsKZck re3fsRq8FCJkM1DPrmceCXRo84+cQsI5tVAY8d9RMrxu1tCpSyiWhMJ5U6smbwjbDIy9G9/9U f2CX0vNBy6AVAoDe78j57GTXRFu+0QNBPVWNteDs5RS9qierQpcaRcWSCHZ07s6JXd4zdY9B7 2/R+nsgr3WG8GjYihjxqn2sIW9O2sOLntrD/ezb+cqmC2ftQ1WUiNB+eN/Z1jFgJVlz56oZyd 5xiMy54ZG++mDgCE07y3FDKcqsDVLrUnM3I2LMvwFwsRjPKSIKA4CPjdNWs37zV38V1Xd8G/s nhq8ArJ+2IMJXJX28Sa9Fvi93CYpAWGLxqWEpD9WBdgeUKhC0fNSyWK4Cy15mvK4RaRE= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt 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 Signed-off-by: Arnd Bergmann Acked-by: Russell King --- 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 */ -- 2.7.0