nptl: Remove futex_supports_exact_relative_timeouts

The only implementation of futex_supports_exact_relative_timeouts always
returns true. Let's remove it and all its callers.

	* nptl/pthread_cond_wait.c: (__pthread_cond_clockwait): Remove code
	that is only useful if futex_supports_exact_relative_timeouts ()
	returns false.
	* nptl/pthread_condattr_setclock.c: (pthread_condattr_setclock):
	Likewise.
	* sysdeps/nptl/futex-internal.h: Remove comment about relative
	timeouts potentially being imprecise since it's no longer true.
	Remove declaration of futex_supports_exact_relative_timeouts.
	* sysdeps/unix/sysv/linux/futex-internal.h: Remove implementation
	of futex_supports_exact_relative_timeouts.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

5 files changed, 12 insertions, 26 deletions

diff --git a/ChangeLog b/ChangeLog
index 9eb8263250..bd57a815b0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2019-07-12  Mike Crowe  <mac@mcrowe.com>
 
+	* nptl/pthread_cond_wait.c: (__pthread_cond_clockwait): Remove code
+	that is only useful if futex_supports_exact_relative_timeouts ()
+	returns false.
+	* nptl/pthread_condattr_setclock.c: (pthread_condattr_setclock):
+	Likewise.
+	* sysdeps/nptl/futex-internal.h: Remove comment about relative
+	timeouts potentially being imprecise since it's no longer true.
+	Remove declaration of futex_supports_exact_relative_timeouts.
+	* sysdeps/unix/sysv/linux/futex-internal.h: Remove implementation
+	of futex_supports_exact_relative_timeouts.
+
 	* NEWS: Mention recently-added pthread_cond_clockwait,
 	pthread_rwlock_clockrdlock, pthread_rwlock_clockwrlock and
 	sem_clockwait functions.
diff --git a/nptl/pthread_cond_wait.c b/nptl/pthread_cond_wait.c
index 68ec754003..450bf66b34 100644
--- a/nptl/pthread_cond_wait.c
+++ b/nptl/pthread_cond_wait.c
@@ -674,11 +674,6 @@ __pthread_cond_clockwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
   if (!futex_abstimed_supported_clockid (clockid))
     return EINVAL;
 
-  /* If we do not support waiting using CLOCK_MONOTONIC, return an error.  */
-  if (clockid == CLOCK_MONOTONIC
-      && !futex_supports_exact_relative_timeouts ())
-    return EINVAL;
-
   return __pthread_cond_wait_common (cond, mutex, clockid, abstime);
 }
 weak_alias (__pthread_cond_clockwait, pthread_cond_clockwait);
diff --git a/nptl/pthread_condattr_setclock.c b/nptl/pthread_condattr_setclock.c
index 641a041fca..ac91923522 100644
--- a/nptl/pthread_condattr_setclock.c
+++ b/nptl/pthread_condattr_setclock.c
@@ -33,11 +33,6 @@ pthread_condattr_setclock (pthread_condattr_t *attr, clockid_t clock_id)
        in the pthread_cond_t structure needs to be adjusted.  */
     return EINVAL;
 
-  /* If we do not support waiting using CLOCK_MONOTONIC, return an error.  */
-  if (clock_id == CLOCK_MONOTONIC
-      && !futex_supports_exact_relative_timeouts())
-    return ENOTSUP;
-
   /* Make sure the value fits in the bits we reserved.  */
   assert (clock_id < (1 << COND_CLOCK_BITS));
 
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
index f29d6d48b2..dff2317b07 100644
--- a/sysdeps/nptl/futex-internal.h
+++ b/sysdeps/nptl/futex-internal.h
@@ -51,8 +51,7 @@
    Both absolute and relative timeouts can be used.  An absolute timeout
    expires when the given specific point in time on the specified clock
    passes, or when it already has passed.  A relative timeout expires when
-   the given duration of time on the CLOCK_MONOTONIC clock passes.  Relative
-   timeouts may be imprecise (see futex_supports_exact_relative_timeouts).
+   the given duration of time on the CLOCK_MONOTONIC clock passes.
 
    Due to POSIX requirements on when synchronization data structures such
    as mutexes or semaphores can be destroyed and due to the futex design
@@ -81,12 +80,6 @@
 static __always_inline int
 futex_supports_pshared (int pshared);
 
-/* Returns true if relative timeouts are robust to concurrent changes to the
-   system clock.  If this returns false, relative timeouts can still be used
-   but might be effectively longer or shorter than requested.  */
-static __always_inline bool
-futex_supports_exact_relative_timeouts (void);
-
 /* Atomically wrt other futex operations on the same futex, this blocks iff
    the value *FUTEX_WORD matches the expected value.  This is
    semantically equivalent to:
diff --git a/sysdeps/unix/sysv/linux/futex-internal.h b/sysdeps/unix/sysv/linux/futex-internal.h
index 299d2489f9..980b7987c3 100644
--- a/sysdeps/unix/sysv/linux/futex-internal.h
+++ b/sysdeps/unix/sysv/linux/futex-internal.h
@@ -46,14 +46,6 @@ futex_supports_pshared (int pshared)
     return EINVAL;
 }
 
-/* The Linux kernel supports relative timeouts measured against the
-   CLOCK_MONOTONIC clock.  */
-static __always_inline bool
-futex_supports_exact_relative_timeouts (void)
-{
-  return true;
-}
-
 /* See sysdeps/nptl/futex-internal.h for details.  */
 static __always_inline int
 futex_wait (unsigned int *futex_word, unsigned int expected, int private)