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MIPS: Allow kernel use of LL/SC to be separate from the presence of LL/SC.

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On some CPUs, it is more efficient to disable and enable interrupts in the
kernel rather than use ll/sc for atomic operations.  But if we were to set
cpu_has_llsc to false, we would break the userspace futex interface (in
asm/futex.h).

We separate the two concepts, with a new predicate kernel_uses_llsc, that
lets us disable the kernel's use of ll/sc while still allowing the futex
code to use it.

Also there were a couple of cases in bitops.h where we were using ll/sc
unconditionally even if cpu_has_llsc were false.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
David Daney
2009-07-13 11:15:19 -07:00
committed by Ralf Baechle
parent f7ade3c168
commit b791d1193a
6 changed files with 50 additions and 47 deletions
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4
arch/mips/include/asm/cmpxchg.h
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@@ -16,7 +16,7 @@
({ \
__typeof(*(m)) __ret; \
\
if (cpu_has_llsc && R10000_LLSC_WAR) { \
if (kernel_uses_llsc && R10000_LLSC_WAR) { \
__asm__ __volatile__( \
" .set push \n" \
" .set noat \n" \
@@ -33,7 +33,7 @@
: "=&r" (__ret), "=R" (*m) \
: "R" (*m), "Jr" (old), "Jr" (new) \
: "memory"); \
} else if (cpu_has_llsc) { \
} else if (kernel_uses_llsc) { \
__asm__ __volatile__( \
" .set push \n" \
" .set noat \n" \