[PATCH] powerpc: use lwsync in atomics, bitops, lock functions

eieio is only a store - store ordering. When used to order an unlock
operation loads may leak out of the critical region. This is potentially
buggy, one example is if a user wants to atomically read a couple of
values.

We can solve this with an lwsync which orders everything except store - load.

I removed the (now unused) EIEIO_ON_SMP macros and the c versions
isync_on_smp and eieio_on_smp now we dont use them. I also removed some
old comments that were used to identify inline spinlocks in assembly,
they dont make sense now our locks are out of line.

Another interesting thing was that read_unlock was using an eieio even
though the rest of the spinlock code had already been converted to
use lwsync.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 10 insertions, 9 deletions

diff --git a/include/asm-powerpc/spinlock.h b/include/asm-powerpc/spinlock.h
index 26b8744ed52..895cb6d3a42 100644
--- a/include/asm-powerpc/spinlock.h
+++ b/include/asm-powerpc/spinlock.h
@@ -46,7 +46,7 @@ static __inline__ unsigned long __spin_trylock(raw_spinlock_t *lock)
 
         token = LOCK_TOKEN;
         __asm__ __volatile__(
-"1:     lwarx           %0,0,%2         # __spin_trylock\n\
+"1:     lwarx           %0,0,%2\n\
         cmpwi           0,%0,0\n\
         bne-            2f\n\
         stwcx.          %1,0,%2\n\
@@ -124,8 +124,8 @@ static void __inline__ __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long
 
 static __inline__ void __raw_spin_unlock(raw_spinlock_t *lock)
 {
-        __asm__ __volatile__(SYNC_ON_SMP"       # __raw_spin_unlock"
-                             : : :"memory");
+        __asm__ __volatile__("# __raw_spin_unlock\n\t"
+                                LWSYNC_ON_SMP: : :"memory");
         lock->slock = 0;
 }
 
@@ -167,7 +167,7 @@ static long __inline__ __read_trylock(raw_rwlock_t *rw)
         long tmp;
 
         __asm__ __volatile__(
-"1:     lwarx           %0,0,%1         # read_trylock\n"
+"1:     lwarx           %0,0,%1\n"
         __DO_SIGN_EXTEND
 "       addic.          %0,%0,1\n\
         ble-            2f\n"
@@ -192,7 +192,7 @@ static __inline__ long __write_trylock(raw_rwlock_t *rw)
 
         token = WRLOCK_TOKEN;
         __asm__ __volatile__(
-"1:     lwarx           %0,0,%2 # write_trylock\n\
+"1:     lwarx           %0,0,%2\n\
         cmpwi           0,%0,0\n\
         bne-            2f\n"
         PPC405_ERR77(0,%1)
@@ -249,8 +249,9 @@ static void __inline__ __raw_read_unlock(raw_rwlock_t *rw)
         long tmp;
 
         __asm__ __volatile__(
-        "eieio                          # read_unlock\n\
-1:      lwarx           %0,0,%1\n\
+        "# read_unlock\n\t"
+        LWSYNC_ON_SMP
+"1:     lwarx           %0,0,%1\n\
         addic           %0,%0,-1\n"
         PPC405_ERR77(0,%1)
 "       stwcx.          %0,0,%1\n\
@@ -262,8 +263,8 @@ static void __inline__ __raw_read_unlock(raw_rwlock_t *rw)
 
 static __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
 {
-        __asm__ __volatile__(SYNC_ON_SMP"       # write_unlock"
-                             : : :"memory");
+        __asm__ __volatile__("# write_unlock\n\t"
+                                LWSYNC_ON_SMP: : :"memory");
         rw->lock = 0;
 }