[S390,PPC] Implement FUTEX_WAIT_BITSET for timedwait functions

Since the FUTEX_WAIT operation takes a relative timeout, the
pthread_cond_timedwait and other timed function implementations have
to get a relative timeout from the absolute timeout parameter it gets
before it makes the futex syscall.  This value is then converted back
into an absolute timeout within the kernel.  This is a waste and has
hence been improved upon by a FUTEX_WAIT_BITSET operation (OR'd with
FUTEX_CLOCK_REALTIME to make the kernel use the realtime clock instead
of the default monotonic clock).  This was implemented only in the x86
and sh assembly code and not in the C code.  This patch implements
support for FUTEX_WAIT_BITSET whenever available (since linux-2.6.29)
for s390 and powerpc.

1 files changed, 20 insertions, 1 deletions

diff --git a/nptl/pthread_rwlock_timedrdlock.c b/nptl/pthread_rwlock_timedrdlock.c
index be8216d579..b7622abfa2 100644
--- a/nptl/pthread_rwlock_timedrdlock.c
+++ b/nptl/pthread_rwlock_timedrdlock.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2003,2004,2007,2011 Free Software Foundation, Inc.
+/* Copyright (C) 2003-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
 
@@ -76,6 +76,16 @@ pthread_rwlock_timedrdlock (rwlock, abstime)
 	  break;
 	}
 
+      /* Work around the fact that the kernel rejects negative timeout values
+	 despite them being valid.  */
+      if (__builtin_expect (abstime->tv_sec < 0, 0))
+	{
+	  result = ETIMEDOUT;
+	  break;
+	}
+
+#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
+     || !defined lll_futex_timed_wait_bitset)
       /* Get the current time.  So far we support only one clock.  */
       struct timeval tv;
       (void) gettimeofday (&tv, NULL);
@@ -96,6 +106,7 @@ pthread_rwlock_timedrdlock (rwlock, abstime)
 	  result = ETIMEDOUT;
 	  break;
 	}
+#endif
 
       /* Remember that we are a reader.  */
       if (++rwlock->__data.__nr_readers_queued == 0)
@@ -112,8 +123,16 @@ pthread_rwlock_timedrdlock (rwlock, abstime)
       lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
       /* Wait for the writer to finish.  */
+#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
+     || !defined lll_futex_timed_wait_bitset)
       err = lll_futex_timed_wait (&rwlock->__data.__readers_wakeup,
 				  waitval, &rt, rwlock->__data.__shared);
+#else
+      err = lll_futex_timed_wait_bitset (&rwlock->__data.__readers_wakeup,
+					 waitval, abstime,
+					 FUTEX_CLOCK_REALTIME,
+					 rwlock->__data.__shared);
+#endif
 
       /* Get the lock.  */
       lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);