From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Fri, 11 Sep 2015 07:34:52 +0000 (+0100)
Subject: ARM: domains: add memory dependencies to get_domain/set_domain
X-Git-Tag: v4.9.8~3513^2~4^2~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6e8f580d1fcc18e290713984c379cb97131c015a;p=platform%2Fkernel%2Flinux-rpi3.git

ARM: domains: add memory dependencies to get_domain/set_domain

We need to have memory dependencies on get_domain/set_domain to avoid
the compiler over-optimising these inline assembly instructions.

Loads/stores must not be reordered across a set_domain(), so introduce
a compiler barrier for that assembly.

The value of get_domain() must not be cached across a set_domain(), but
we still want to allow the compiler to optimise it away.  Introduce a
dependency on current_thread_info()->cpu_domain to avoid this; the new
memory clobber in set_domain() should therefore cause the compiler to
re-load this.  The other advantage of using this is we should have its
address in the register set already, or very soon after at most call
sites.

Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---

diff --git a/arch/arm/include/asm/domain.h b/arch/arm/include/asm/domain.h
index e878129..fc8ba16 100644
--- a/arch/arm/include/asm/domain.h
+++ b/arch/arm/include/asm/domain.h
@@ -12,6 +12,7 @@
 
 #ifndef __ASSEMBLY__
 #include <asm/barrier.h>
+#include <asm/thread_info.h>
 #endif
 
 /*
@@ -89,7 +90,8 @@ static inline unsigned int get_domain(void)
 
 	asm(
 	"mrc	p15, 0, %0, c3, c0	@ get domain"
-	 : "=r" (domain));
+	 : "=r" (domain)
+	 : "m" (current_thread_info()->cpu_domain));
 
 	return domain;
 }
@@ -98,7 +100,7 @@ static inline void set_domain(unsigned val)
 {
 	asm volatile(
 	"mcr	p15, 0, %0, c3, c0	@ set domain"
-	  : : "r" (val));
+	  : : "r" (val) : "memory");
 	isb();
 }