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nptl: Remove futex_supports_exact_relative_timeouts

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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>
This commit is contained in:
Mike Crowe 2019-06-24 20:18:00 +00:00 committed by Adhemerval Zanella
parent 65dd7e9ce3
commit 1ff1373b33
5 changed files with 12 additions and 26 deletions
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11
ChangeLog
View File

@ -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.

5
nptl/pthread_cond_wait.c
View File

@ -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);

5
nptl/pthread_condattr_setclock.c
View File

@ -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));

9
sysdeps/nptl/futex-internal.h
View File

@ -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:

8
sysdeps/unix/sysv/linux/futex-internal.h
View File

@ -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)