[PARISC] Only write to memory in test_and_set_bit/test_and_clear_bit if we're

going to change the bit.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 14 insertions, 8 deletions

diff --git a/include/asm-parisc/bitops.h b/include/asm-parisc/bitops.h
index 900561922c4c..9577342f21aa 100644
--- a/include/asm-parisc/bitops.h
+++ b/include/asm-parisc/bitops.h
@@ -60,31 +60,37 @@ static __inline__ void change_bit(int nr, volatile unsigned long * addr)
 static __inline__ int test_and_set_bit(int nr, volatile unsigned long * addr)
 {
         unsigned long mask = 1UL << CHOP_SHIFTCOUNT(nr);
-        unsigned long oldbit;
+        unsigned long old;
         unsigned long flags;
+        int set;
 
         addr += (nr >> SHIFT_PER_LONG);
         _atomic_spin_lock_irqsave(addr, flags);
-        oldbit = *addr;
-        *addr = oldbit | mask;
+        old = *addr;
+        set = (old & mask) ? 1 : 0;
+        if (!set)
+                *addr = old | mask;
         _atomic_spin_unlock_irqrestore(addr, flags);
 
-        return (oldbit & mask) ? 1 : 0;
+        return set;
 }
 
 static __inline__ int test_and_clear_bit(int nr, volatile unsigned long * addr)
 {
         unsigned long mask = 1UL << CHOP_SHIFTCOUNT(nr);
-        unsigned long oldbit;
+        unsigned long old;
         unsigned long flags;
+        int set;
 
         addr += (nr >> SHIFT_PER_LONG);
         _atomic_spin_lock_irqsave(addr, flags);
-        oldbit = *addr;
-        *addr = oldbit & ~mask;
+        old = *addr;
+        set = (old & mask) ? 1 : 0;
+        if (set)
+                *addr = old & ~mask;
         _atomic_spin_unlock_irqrestore(addr, flags);
 
-        return (oldbit & mask) ? 1 : 0;
+        return set;
 }
 
 static __inline__ int test_and_change_bit(int nr, volatile unsigned long * addr)