unify and overhaul timed futex waits

new features:

- FUTEX_WAIT_BITSET op will be used for timed waits if available. this
  saves a call to clock_gettime.

- error checking for the timespec struct is now inside __timedwait so
  it doesn't need to be duplicated everywhere. cond_timedwait still
  needs to duplicate it to avoid unlocking the mutex, though.

- pushing and popping the cancellation handler is delegated to
  __timedwait, and cancellable/non-cancellable waits are unified.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/internal/futex.h b/src/internal/futex.h
index c0453822..d7bf2b7d 100644
--- a/src/internal/futex.h
+++ b/src/internal/futex.h
@@ -10,6 +10,9 @@
 #define FUTEX_LOCK_PI		6
 #define FUTEX_UNLOCK_PI		7
 #define FUTEX_TRYLOCK_PI	8
+#define FUTEX_WAIT_BITSET	9
+
+#define FUTEX_CLOCK_REALTIME 256
 
 int __futex(volatile int *, int, int, void *);