fix missing barrier instructions in mips atomic asm

previously I had wrongly assumed the ll/sc instructions also provided
memory synchronization; apparently they do not. this commit adds sync
instructions before and after each atomic operation and changes the
atomic store to simply use sync before and after a plain store, rather
than a useless compare-and-swap.

(cherry picked from commit bcad48439494820989f5867c3f8ccfa6aae2909f)

diff --git a/arch/mips/atomic.h b/arch/mips/atomic.h
index 6731d17bd79b020dbc99873250bdad7be478f3ce..9dcd1555af68dd434a1bea5976837c26c57cb993 100644 (file)
--- a/arch/mips/atomic.h
+++ b/arch/mips/atomic.h
@@ -29,12 +29,14 @@ static inline int a_cas(volatile int *p, int t, int s)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %2\n"
                "       bne %0, %3, 1f\n"
                "       addu %1, %4, $0\n"
                "       sc %1, %2\n"
                "       beq %1, $0, 1b\n"
                "       nop\n"
+               "       sync\n"
                "1:     \n"
                ".set pop\n"
                : "=&r"(t), "=&r"(dummy), "+m"(*p) : "r"(t), "r"(s) : "memory" );
@@ -59,12 +61,13 @@ static inline int a_swap(volatile int *x, int v)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %2\n"
                "       addu %1, %3, $0\n"
                "       sc %1, %2\n"
                "       beq %1, $0, 1b\n"
                "       nop\n"
-               "1:     \n"
+               "       sync\n"
                ".set pop\n"
                : "=&r"(old), "=&r"(dummy), "+m"(*x) : "r"(v) : "memory" );
         return old;
@@ -77,12 +80,13 @@ static inline int a_fetch_add(volatile int *x, int v)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %2\n"
                "       addu %1, %0, %3\n"
                "       sc %1, %2\n"
                "       beq %1, $0, 1b\n"
                "       nop\n"
-               "1:     \n"
+               "       sync\n"
                ".set pop\n"
                : "=&r"(old), "=&r"(dummy), "+m"(*x) : "r"(v) : "memory" );
         return old;
@@ -95,12 +99,13 @@ static inline void a_inc(volatile int *x)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %1\n"
                "       addu %0, %0, 1\n"
                "       sc %0, %1\n"
                "       beq %0, $0, 1b\n"
                "       nop\n"
-               "1:     \n"
+               "       sync\n"
                ".set pop\n"
                : "=&r"(dummy), "+m"(*x) : : "memory" );
 }
@@ -112,31 +117,28 @@ static inline void a_dec(volatile int *x)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %1\n"
                "       subu %0, %0, 1\n"
                "       sc %0, %1\n"
                "       beq %0, $0, 1b\n"
                "       nop\n"
-               "1:     \n"
+               "       sync\n"
                ".set pop\n"
                : "=&r"(dummy), "+m"(*x) : : "memory" );
 }
 
 static inline void a_store(volatile int *p, int x)
 {
-       int dummy;
        __asm__ __volatile__(
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
-               "1:     ll %0, %1\n"
-               "       addu %0, %2, $0\n"
-               "       sc %0, %1\n"
-               "       beq %0, $0, 1b\n"
-               "       nop\n"
-               "1:     \n"
+               "       sync\n"
+               "       sw %1, %0\n"
+               "       sync\n"
                ".set pop\n"
-               : "=&r"(dummy), "+m"(*p) : "r"(x) : "memory" );
+               : "+m"(*p) : "r"(x) : "memory" );
 }
 
 static inline void a_spin()
@@ -155,12 +157,13 @@ static inline void a_and(volatile int *p, int v)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %1\n"
                "       and %0, %0, %2\n"
                "       sc %0, %1\n"
                "       beq %0, $0, 1b\n"
                "       nop\n"
-               "1:     \n"
+               "       sync\n"
                ".set pop\n"
                : "=&r"(dummy), "+m"(*p) : "r"(v) : "memory" );
 }
@@ -172,12 +175,13 @@ static inline void a_or(volatile int *p, int v)
                ".set push\n"
                ".set mips2\n"
                ".set noreorder\n"
+               "       sync\n"
                "1:     ll %0, %1\n"
                "       or %0, %0, %2\n"
                "       sc %0, %1\n"
                "       beq %0, $0, 1b\n"
                "       nop\n"
-               "1:     \n"
+               "       sync\n"
                ".set pop\n"
                : "=&r"(dummy), "+m"(*p) : "r"(v) : "memory" );
 }