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ARM: 8135/1: Fix in-correct barrier usage in SWP{B} emulation

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According to the ARM ARMv7, explicit barriers are necessary when using
synchronisation primitives such as SWP{B}. The use of these
instructions does not automatically imply a barrier and any ordering
requirements by the software must be explicitly expressed with the use
of suitable barriers.

Based on this, remove the barriers from SWP{B} emulation.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Punit Agrawal 2014-09-01 17:16:01 +01:00 committed by Russell King
parent a040803a9d
commit e918a62a2b
1 changed files with 0 additions and 15 deletions
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15
arch/arm/kernel/swp_emulate.c
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@ -142,14 +142,6 @@ static int emulate_swpX(unsigned int address, unsigned int *data,
while (1) {
unsigned long temp;
/*
* Barrier required between accessing protected resource and
* releasing a lock for it. Legacy code might not have done
* this, and we cannot determine that this is not the case
* being emulated, so insert always.
*/
smp_mb();
if (type == TYPE_SWPB)
__user_swpb_asm(*data, address, res, temp);
else
@ -162,13 +154,6 @@ static int emulate_swpX(unsigned int address, unsigned int *data,
}
if (res == 0) {
/*
* Barrier also required between acquiring a lock for a
* protected resource and accessing the resource. Inserted for
* same reason as above.
*/
smp_mb();
if (type == TYPE_SWPB)
swpbcounter++;
else