MIPS: Allow kernel use of LL/SC to be separate from the presence of LL/SC.
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>
diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index 8ab1d12..1f4df64 100644
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -80,6 +80,9 @@
#ifndef cpu_has_llsc
#define cpu_has_llsc (cpu_data[0].options & MIPS_CPU_LLSC)
#endif
+#ifndef kernel_uses_llsc
+#define kernel_uses_llsc cpu_has_llsc
+#endif
#ifndef cpu_has_mips16
#define cpu_has_mips16 (cpu_data[0].ases & MIPS_ASE_MIPS16)
#endif