| Message ID | 1395330874-4876-1-git-send-email-kamal@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index b4ca707..d429475 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -44,18 +44,9 @@ static inline void dsb_sev(void) { -#if __LINUX_ARM_ARCH__ >= 7 - __asm__ __volatile__ ( - "dsb\n" - SEV - ); -#else - __asm__ __volatile__ ( - "mcr p15, 0, %0, c7, c10, 4\n" - SEV - : : "r" (0) - ); -#endif + + dsb(ishst); + __asm__(SEV); } /*
This is a note to let you know that I have just added a patch titled ARM: 7955/1: spinlock: ensure we have a compiler barrier before sev to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.20. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From b40a702efef22eed3d41f35c2f219d587c22afb0 Mon Sep 17 00:00:00 2001 From: Will Deacon <will.deacon@arm.com> Date: Fri, 7 Feb 2014 19:12:32 +0100 Subject: ARM: 7955/1: spinlock: ensure we have a compiler barrier before sev commit 7c8746a9eb287642deaad0e7c2cdf482dce5e4be upstream. When unlocking a spinlock, we require the following, strictly ordered sequence of events: <barrier> /* dmb */ <unlock> <barrier> /* dsb */ <sev> Whilst the code does indeed reflect this in terms of the architecture, the final <barrier> + <sev> have been contracted into a single inline asm without a "memory" clobber, therefore the compiler is at liberty to reorder the unlock to the end of the above sequence. In such a case, a waiting CPU may be woken up before the lock has been unlocked, leading to extremely poor performance. This patch reworks the dsb_sev() function to make use of the dsb() macro and ensure ordering against the unlock. Reported-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/arm/include/asm/spinlock.h | 15 +++------------ 1 file changed, 3 insertions(+), 12 deletions(-) -- 1.8.3.2