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>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/mips/include/asm/system.h b/arch/mips/include/asm/system.h
index cc7262ff0765..fcf5f98d90cc 100644
--- a/arch/mips/include/asm/system.h
+++ b/arch/mips/include/asm/system.h
@@ -94,7 +94,7 @@ static inline unsigned long __xchg_u32(volatile int * m, unsigned int val)
 {
         __u32 retval;
 
-        if (cpu_has_llsc && R10000_LLSC_WAR) {
+        if (kernel_uses_llsc && R10000_LLSC_WAR) {
                 unsigned long dummy;
 
                 __asm__ __volatile__(
@@ -109,7 +109,7 @@ static inline unsigned long __xchg_u32(volatile int * m, unsigned int val)
                 : "=&r" (retval), "=m" (*m), "=&r" (dummy)
                 : "R" (*m), "Jr" (val)
                 : "memory");
-        } else if (cpu_has_llsc) {
+        } else if (kernel_uses_llsc) {
                 unsigned long dummy;
 
                 __asm__ __volatile__(
@@ -146,7 +146,7 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val)
 {
         __u64 retval;
 
-        if (cpu_has_llsc && R10000_LLSC_WAR) {
+        if (kernel_uses_llsc && R10000_LLSC_WAR) {
                 unsigned long dummy;
 
                 __asm__ __volatile__(
@@ -159,7 +159,7 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val)
                 : "=&r" (retval), "=m" (*m), "=&r" (dummy)
                 : "R" (*m), "Jr" (val)
                 : "memory");
-        } else if (cpu_has_llsc) {
+        } else if (kernel_uses_llsc) {
                 unsigned long dummy;
 
                 __asm__ __volatile__(