releases/2.6.34.6/sparc64-fix-rwsem-constant-bug-leading-to-hangs.patch

   1 From f23bfe840d9dee81b3be25eb3fd5e715b4fdee5a Mon Sep 17 00:00:00 2001
   2 From: David S. Miller <davem@davemloft.net>
   3 Date: Tue, 17 Aug 2010 17:09:53 -0700
   4 Subject: sparc64: Fix rwsem constant bug leading to hangs.
   5
   6 From: David S. Miller <davem@davemloft.net>
   7
   8 [ Upstream commit ef201bebe5afc91a2b99b45dacc8c6dd88ca9e58 ]
   9
  10 As noticed by Linus, it is critical that some of the
  11 rwsem constants be signed.  Yet, hex constants are
  12 unsigned unless explicitly casted or negated.
  13
  14 The most critical one is RWSEM_WAITING_BIAS.
  15
  16 This bug was exacerbated by commit
  17 424acaaeb3a3932d64a9b4bd59df6cf72c22d8f3 ("rwsem: wake queued readers
  18 when writer blocks on active read lock")
  19
  20 Signed-off-by: David S. Miller <davem@davemloft.net>
  21 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  22 ---
  23  arch/sparc/include/asm/rwsem-const.h |    2 +-
  24  1 file changed, 1 insertion(+), 1 deletion(-)
  25
  26 --- a/arch/sparc/include/asm/rwsem-const.h
  27 +++ b/arch/sparc/include/asm/rwsem-const.h
  28 @@ -5,7 +5,7 @@
  29  #define RWSEM_UNLOCKED_VALUE           0x00000000
  30  #define RWSEM_ACTIVE_BIAS              0x00000001
  31  #define RWSEM_ACTIVE_MASK              0x0000ffff
  32 -#define RWSEM_WAITING_BIAS             0xffff0000
  33 +#define RWSEM_WAITING_BIAS             (-0x00010000)
  34  #define RWSEM_ACTIVE_READ_BIAS         RWSEM_ACTIVE_BIAS
  35  #define RWSEM_ACTIVE_WRITE_BIAS                (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
  36