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Introduce pthread_condattr_setclock()

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This is one of the few POSIX APIs that was missing. It lets you choose a
monotonic clock for your condition variables. This might improve perf on
some platforms. It might also grant more flexibility with NTP configs. I
know Qt is one project that believes it needs this. To introduce this, I
needed to change some the *NSYNC APIs, to support passing a clock param.
There's also new benchmarks, demonstrating Cosmopolitan's supremacy over
many libc implementations when it comes to mutex performance. Cygwin has
an alarmingly bad pthread_mutex_t implementation. It is so bad that they
would have been significantly better off if they'd used naive spinlocks.
This commit is contained in:
Justine Tunney 2024-09-02 23:37:50 -07:00
parent 79516bf08e
commit 3c61a541bd
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GPG key ID: BE714B4575D6E328
55 changed files with 449 additions and 155 deletions
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6
libc/intrin/pthread_mutex_lock.c
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@ -57,12 +57,12 @@ static void pthread_mutex_lock_drepper(atomic_int *futex, char pshare) {
LOCKTRACE("acquiring pthread_mutex_lock_drepper(%t)...", futex);
if (word == 1)
word = atomic_exchange_explicit(futex, 2, memory_order_acquire);
BLOCK_CANCELATION;
while (word > 0) {
BLOCK_CANCELATION;
_weaken(nsync_futex_wait_)(futex, 2, pshare, 0);
ALLOW_CANCELATION;
_weaken(nsync_futex_wait_)(futex, 2, pshare, 0, 0);
word = atomic_exchange_explicit(futex, 2, memory_order_acquire);
}
ALLOW_CANCELATION;
}
static errno_t pthread_mutex_lock_recursive(pthread_mutex_t *mutex,