Add adaptive elision to rwlocks

This patch relies on the C version of the rwlocks posted earlier.
With C rwlocks it is very straight forward to do adaptive elision
using TSX. It is based on the infrastructure added earlier
for mutexes, but uses its own elision macros. The macros
are fairly general purpose and could be used for other
elision purposes too.

This version is much cleaner than the earlier assembler based
version, and in particular implements adaptation which makes
it safer.

I changed the behavior slightly to not require any changes
in the test suite and fully conform to all expected
behaviors (generally at the cost of not eliding in
various situations). In particular this means the timedlock
variants are not elided.  Nested trylock aborts.

1 files changed, 5 insertions, 2 deletions

diff --git a/sysdeps/x86/nptl/bits/pthreadtypes.h b/sysdeps/x86/nptl/bits/pthreadtypes.h
index b4329f652b..b04c32b11f 100644
--- a/sysdeps/x86/nptl/bits/pthreadtypes.h
+++ b/sysdeps/x86/nptl/bits/pthreadtypes.h
@@ -184,11 +184,13 @@ typedef union
     unsigned int __nr_writers_queued;
     int __writer;
     int __shared;
-    unsigned long int __pad1;
+    signed char __rwelision;
+    unsigned char __pad1[7];
     unsigned long int __pad2;
     /* FLAGS must stay at this position in the structure to maintain
        binary compatibility.  */
     unsigned int __flags;
+# define __PTHREAD_RWLOCK_ELISION_EXTRA 0, {0, 0, 0, 0, 0, 0, 0 }
 # define __PTHREAD_RWLOCK_INT_FLAGS_SHARED	1
   } __data;
 # else
@@ -204,7 +206,8 @@ typedef union
        binary compatibility.  */
     unsigned char __flags;
     unsigned char __shared;
-    unsigned char __pad1;
+    signed char __rwelision;
+# define __PTHREAD_RWLOCK_ELISION_EXTRA 0
     unsigned char __pad2;
     int __writer;
   } __data;