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ARM: domains: add memory dependencies to get_domain/set_domain

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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>
This commit is contained in:
Russell King 2015-09-11 08:34:52 +01:00
parent 716ff1921a
commit 6e8f580d1f
1 changed files with 4 additions and 2 deletions
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6
arch/arm/include/asm/domain.h
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@ -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();
}