sparc64: Fix rwsem constant bug leading to hangs.

As noticed by Linus, it is critical that some of the
rwsem constants be signed.  Yet, hex constants are
unsigned unless explicitly casted or negated.

The most critical one is RWSEM_WAITING_BIAS.

This bug was exacerbated by commit
424acaaeb3a3932d64a9b4bd59df6cf72c22d8f3 ("rwsem: wake queued readers
when writer blocks on active read lock")

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc/include/asm/rwsem-const.h b/arch/sparc/include/asm/rwsem-const.h
index a303c9d..e4c61a1 100644 (file)
--- a/arch/sparc/include/asm/rwsem-const.h
+++ b/arch/sparc/include/asm/rwsem-const.h
@@ -5,7 +5,7 @@
 #define RWSEM_UNLOCKED_VALUE           0x00000000
 #define RWSEM_ACTIVE_BIAS              0x00000001
 #define RWSEM_ACTIVE_MASK              0x0000ffff
-#define RWSEM_WAITING_BIAS             0xffff0000
+#define RWSEM_WAITING_BIAS             (-0x00010000)
 #define RWSEM_ACTIVE_READ_BIAS         RWSEM_ACTIVE_BIAS
 #define RWSEM_ACTIVE_WRITE_BIAS                (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)