nptl: Replace non cancellable pause/nanosleep with futex

To help y2038 work avoid duplicate all the logic of nanosleep on
non cancellable version, the patch replace it with a new futex
operation, lll_timedwait.  The changes are:

  - Add a expected value for __lll_clocklock_wait, so it can be used
    to wait for generic values.

  - Remove its internal atomic operation and move the logic to
    __lll_clocklock.  It makes __lll_clocklock_wait even more generic
    and __lll_clocklock slight faster on fast-path (since it won't
    require a function call anymore).

  - Add lll_timedwait, which uses __lll_clocklock_wait, to replace both
    __pause_nocancel and __nanosleep_nocancel.

It also allows remove the sparc32 __lll_clocklock_wait implementation
(since it is similar to the generic one).

Checked on x86_64-linux-gnu, sparcv9-linux-gnu, and i686-linux-gnu.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

3 files changed, 23 insertions, 35 deletions

diff --git a/nptl/lll_timedlock_wait.c b/nptl/lll_timedlock_wait.c
index cd3cc3d..952b042 100644
--- a/nptl/lll_timedlock_wait.c
+++ b/nptl/lll_timedlock_wait.c
@@ -25,39 +25,38 @@
 
 
 int
-__lll_clocklock_wait (int *futex, clockid_t clockid,
+__lll_clocklock_wait (int *futex, int val, clockid_t clockid,
 		      const struct timespec *abstime, int private)
 {
-  /* Reject invalid timeouts.  */
-  if (! valid_nanoseconds (abstime->tv_nsec))
-    return EINVAL;
+  struct timespec ts, *tsp = NULL;
 
-  /* Try locking.  */
-  while (atomic_exchange_acq (futex, 2) != 0)
+  if (abstime != NULL)
     {
-      struct timespec ts;
+      /* Reject invalid timeouts.  */
+      if (! valid_nanoseconds (abstime->tv_nsec))
+        return EINVAL;
 
-      /* Get the current time. This can only fail if clockid is not
-         valid.  */
+      /* Get the current time. This can only fail if clockid is not valid.  */
       if (__glibc_unlikely (__clock_gettime (clockid, &ts) != 0))
         return EINVAL;
 
       /* Compute relative timeout.  */
-      struct timespec rt;
-      rt.tv_sec = abstime->tv_sec - ts.tv_sec;
-      rt.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
-      if (rt.tv_nsec < 0)
+      ts.tv_sec = abstime->tv_sec - ts.tv_sec;
+      ts.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
+      if (ts.tv_nsec < 0)
         {
-          rt.tv_nsec += 1000000000;
-          --rt.tv_sec;
+	  ts.tv_nsec += 1000000000;
+	  --ts.tv_sec;
         }
 
-      if (rt.tv_sec < 0)
+      if (ts.tv_sec < 0)
         return ETIMEDOUT;
 
-      /* If *futex == 2, wait until woken or timeout.  */
-      lll_futex_timed_wait (futex, 2, &rt, private);
+      tsp = &ts;
     }
 
+  /* If *futex == val, wait until woken or timeout.  */
+  lll_futex_timed_wait (futex, val, tsp, private);
+
   return 0;
 }
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 0ab890d..ace436d 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -434,7 +434,8 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
 
 		/* Delay the thread indefinitely.  */
 		while (1)
-		  __pause_nocancel ();
+		  lll_timedwait (&(int){0}, 0, 0 /* ignored */, NULL,
+				 private);
 	      }
 
 	    oldval = mutex->__data.__lock;
diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index d6f0d9e..76b93bd 100644
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -401,22 +401,10 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
 
 		    /* Delay the thread until the timeout is reached.
 		       Then return ETIMEDOUT.  */
-		    struct timespec reltime;
-		    struct timespec now;
-
-		    INTERNAL_SYSCALL (clock_gettime, __err, 2, clockid,
-				      &now);
-		    reltime.tv_sec = abstime->tv_sec - now.tv_sec;
-		    reltime.tv_nsec = abstime->tv_nsec - now.tv_nsec;
-		    if (reltime.tv_nsec < 0)
-		      {
-			reltime.tv_nsec += 1000000000;
-			--reltime.tv_sec;
-		      }
-		    if (reltime.tv_sec >= 0)
-		      while (__nanosleep_nocancel (&reltime, &reltime) != 0)
-			continue;
-
+		    do
+		      e = lll_timedwait (&(int){0}, 0, clockid, abstime,
+					 private);
+		    while (e != ETIMEDOUT);
 		    return ETIMEDOUT;
 		  }