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[PATCH 0/7] Implement proposed POSIX _clockwait variants of existing _timedwait functions
- From: Mike Crowe <mac at mcrowe dot com>
- To: libc-alpha at sourceware dot org
- Cc: Mike Crowe <mac at mcrowe dot com>
- Date: Wed, 27 Feb 2019 18:23:50 +0000
- Subject: [PATCH 0/7] Implement proposed POSIX _clockwait variants of existing _timedwait functions
My attempts[1] to add a variant of pthread_cond_timedwait that would accept
a clockid_t parameter led me to propose[2] to The Austin Group the addition
of an entire family of functions that accept a clockid_t parameter to
indicate the clock that the timespec absolute timeout parameter should be
measured against. They responded positively to the request but an
implementation is required before the proposal can proceed.
This patch series is the first part of that implementation in glibc, it
contains four new functions:
int pthread_cond_clockwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
clockid_t clock, const struct timespec *abstime)
int pthread_rwlock_clockrdlock(pthread_rwlock_t *rwlock, clockid_t clock,
const struct timespec *abstime)
int pthread_rwlock_clockwrlock(pthread_rwlock_t *rwlock, clockid_t clock,
const struct timespec *abstime)
int sem_clockwait(sem_t *restrict, clockid_t clock_id, const struct
timespec *restrict)
These are implemented by replacing the underlying equivalent _timed
functions with ones that accept a clockid_t parameter, and then
implementing the existing _timed functions by passing CLOCK_REALTIME to the
new implementation. This requires clockid_t parameters to be added to the
underlying futex-internal and lowlevellock-futex functions.
pthread_mutex_clocklock is not yet implemented because doing so requires a
version of __lll_timedlock_wait that supports both CLOCK_MONOTONIC and
CLOCK_REALTIME. This function is currently architecture specific. I plan to
work on that next, if these changes are considered acceptable.
The mq_clockreceive and mq_clocksend functions corresponding to
mq_timedreceive and mq_timedsend require kernel changes before they can be
implemented in glibc.
As implemented, passing an unsupported or invalid clock to these functions
yields EINVAL. I considered returning ENOTSUP for valid-but-unsupported
clocks, but I was worried that there was a risk that the list of valid
clocks would not be updated when a new clock was added to glibc.
A number of tests have been updated to use struct timespec rather than
struct timeval so that they can call clock_gettime(CLOCK_MONOTONIC) rather
then gettimeofday. To make this easier I created the support/timespec.h
header file to contain functions to add and subtract timespec structures
borrowed from sysdeps/pthread/posix-timer.h. There's probably a better
place for these, but I don't know where that might be.
Rather than duplicating tests, I've parameterised them so that the same
tests can be run on the existing timedwait functions and the new clockwait
functions.
The changes have been tested with "make check" on x86_64 and arm64. Earlier
versions were tested on arm. I haven't updated the ChangeLog, NEWS or
architecture abilists yet (so some tests fail on arm64), but will do so if
the rest of the changes are acceptable.
Thanks to everyone that commented on previous versions of this patch (when
the single new function was called pthread_cond_timedwaitonclock_np.) They
have been a great help, and I hope that I have incorporated their feedback
correctly.
[1] https://sourceware.org/ml/libc-alpha/2015-07/msg00193.html
[2] http://austingroupbugs.net/view.php?id=1216
Mike Crowe (7):
nptl: Add clockid parameter to futex timed wait calls
nptl: Add POSIX-proposed sem_clockwait
nptl: Add POSIX-proposed pthread_cond_clockwait
nptl: pthread_rwlock: Move timeout validation into _full functions
nptl/tst-rwlock14: Test pthread/rwlock_timedwrlock correctly
nptl/tst-rwlock: Use clock_gettime/timespec rather than gettimeofday/timeval
nptl: Add POSIX-proposed pthread_rwlock_clockrdlock & pthread_rwlock_clockwrlock
conform/data/semaphore.h-data | 1 +-
manual/threads.texi | 58 ++++-
nptl/Makefile | 8 +-
nptl/Versions | 5 +-
nptl/forward.c | 5 +-
nptl/nptl-init.c | 1 +-
nptl/pthreadP.h | 4 +-
nptl/pthread_cond_wait.c | 45 ++-
nptl/pthread_mutex_timedlock.c | 8 +-
nptl/pthread_rwlock_clockrdlock.c | 27 ++-
nptl/pthread_rwlock_clockwrlock.c | 27 ++-
nptl/pthread_rwlock_common.c | 32 +-
nptl/pthread_rwlock_rdlock.c | 2 +-
nptl/pthread_rwlock_timedrdlock.c | 12 +-
nptl/pthread_rwlock_timedwrlock.c | 12 +-
nptl/pthread_rwlock_wrlock.c | 2 +-
nptl/sem_clockwait.c | 45 +++-
nptl/sem_timedwait.c | 3 +-
nptl/sem_wait.c | 3 +-
nptl/sem_waitcommon.c | 15 +-
nptl/tst-abstime.c | 28 ++-
nptl/tst-cond11.c | 30 +-
nptl/tst-cond26.c | 91 +++++++-
nptl/tst-cond27.c | 113 +++++++++-
nptl/tst-rwlock14.c | 159 +++++++++++-
nptl/tst-rwlock6.c | 132 ++++++----
nptl/tst-rwlock7.c | 108 +++++---
nptl/tst-rwlock9.c | 90 +++++--
nptl/tst-sem13.c | 50 +++-
nptl/tst-sem17.c | 57 ++++-
nptl/tst-sem5.c | 30 +-
support/timespec.h | 27 ++-
sysdeps/nptl/futex-internal.h | 7 +-
sysdeps/nptl/lowlevellock-futex.h | 14 +-
sysdeps/nptl/pthread-functions.h | 4 +-
sysdeps/nptl/pthread.h | 21 ++-
sysdeps/pthread/semaphore.h | 4 +-
sysdeps/unix/sysv/linux/futex-internal.h | 26 +-
sysdeps/unix/sysv/linux/lowlevellock-futex.h | 29 +-
sysdeps/unix/sysv/linux/x86_64/64/libpthread.abilist | 4 +-
40 files changed, 1124 insertions(+), 215 deletions(-)
create mode 100644 nptl/pthread_rwlock_clockrdlock.c
create mode 100644 nptl/pthread_rwlock_clockwrlock.c
create mode 100644 nptl/sem_clockwait.c
create mode 100644 nptl/tst-cond26.c
create mode 100644 nptl/tst-cond27.c
create mode 100644 nptl/tst-sem17.c
create mode 100644 support/timespec.h
base-commit: a04549c19407a29a271779598a9518f9baf959e0
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