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Optimize pthread_cond_timedwait to avoid unnecessary call to clock_gettime for CLOCK_MONOTONIC

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This commit is contained in:
Justin King 2024-01-11 18:51:23 +00:00 committed by Pranav Kant
parent 5643a977d0
commit be3c0fe888
5 changed files with 10 additions and 31 deletions
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29
nptl/pthread_cond_wait.c
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@ -510,34 +510,13 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
if (__glibc_unlikely (abstime->tv_sec < 0))
err = ETIMEDOUT;
else if ((flags & __PTHREAD_COND_CLOCK_MONOTONIC_MASK) != 0)
{
/* CLOCK_MONOTONIC is requested. */
struct timespec rt;
if (__clock_gettime (CLOCK_MONOTONIC, &rt) != 0)
__libc_fatal ("clock_gettime does not support "
"CLOCK_MONOTONIC");
/* Convert the absolute timeout value to a relative
timeout. */
rt.tv_sec = abstime->tv_sec - rt.tv_sec;
rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec;
if (rt.tv_nsec < 0)
{
rt.tv_nsec += 1000000000;
--rt.tv_sec;
}
/* Did we already time out? */
if (__glibc_unlikely (rt.tv_sec < 0))
err = ETIMEDOUT;
else
err = futex_reltimed_wait_cancelable
(cond->__data.__g_signals + g, 0, &rt, private);
}
else
{
/* Use CLOCK_REALTIME. */
err = futex_abstimed_wait_cancelable
(cond->__data.__g_signals + g, 0, abstime, private);
(cond->__data.__g_signals + g, 0, abstime,
(flags & __PTHREAD_COND_CLOCK_MONOTONIC_MASK) != 0
? 0
: FUTEX_CLOCK_REALTIME, private);
}
}

4
nptl/sem_waitcommon.c
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@ -110,10 +110,10 @@ do_futex_wait (struct new_sem *sem, const struct timespec *abstime)
#if __HAVE_64B_ATOMICS
err = futex_abstimed_wait_cancelable (
(unsigned int *) &sem->data + SEM_VALUE_OFFSET, 0, abstime,
sem->private);
FUTEX_CLOCK_REALTIME, sem->private);
#else
err = futex_abstimed_wait_cancelable (&sem->value, SEM_NWAITERS_MASK,
abstime, sem->private);
abstime, FUTEX_CLOCK_REALTIME, sem->private);
#endif
return err;

2
sysdeps/nptl/futex-internal.h
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@ -169,7 +169,7 @@ futex_abstimed_wait (unsigned int* futex_word, unsigned int expected,
static __always_inline int
futex_abstimed_wait_cancelable (unsigned int* futex_word,
unsigned int expected,
const struct timespec* abstime, int private);
const struct timespec* abstime, int clockbit, int private);
/* Atomically wrt other futex operations on the same futex, this unblocks the
specified number of processes, or all processes blocked on this futex if

2
sysdeps/sparc/sparc32/sem_waitcommon.c
View File

@ -52,7 +52,7 @@ do_futex_wait (struct new_sem *sem, const struct timespec *abstime)
int err;
err = futex_abstimed_wait_cancelable (&sem->value, SEM_NWAITERS_MASK,
abstime, sem->private);
abstime, FUTEX_CLOCK_REALTIME, sem->private);
return err;
}

4
sysdeps/unix/sysv/linux/futex-internal.h
View File

@ -194,7 +194,7 @@ futex_abstimed_wait (unsigned int *futex_word, unsigned int expected,
static __always_inline int
futex_abstimed_wait_cancelable (unsigned int *futex_word,
unsigned int expected,
const struct timespec *abstime, int private)
const struct timespec *abstime, int clockbit, int private)
{
/* Work around the fact that the kernel rejects negative timeout values
despite them being valid. */
@ -203,7 +203,7 @@ futex_abstimed_wait_cancelable (unsigned int *futex_word,
int oldtype;
oldtype = __pthread_enable_asynccancel ();
int err = lll_futex_timed_wait_bitset (futex_word, expected, abstime,
FUTEX_CLOCK_REALTIME, private);
clockbit, private);
__pthread_disable_asynccancel (oldtype);
switch (err)
{