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Introduce cosmo_futex_wait and cosmo_futex_wake

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Cosmopolitan Futexes are now exposed as a public API.
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Justine Tunney 2024-11-22 11:08:29 -08:00
parent 729f7045e3
commit 9ddbfd921e
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66 changed files with 886 additions and 917 deletions
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libc/intrin/clock_gettime-mono.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/atomic.h"
#include "libc/calls/struct/timespec.h"
#include "libc/calls/struct/timespec.internal.h"
#include "libc/calls/struct/timeval.h"
#include "libc/cosmo.h"
#include "libc/dce.h"
#include "libc/nexgen32e/rdtsc.h"
/**
* @fileoverview Monotonic clock polyfill.
*
* This isn't quite `CLOCK_MONOTONIC` and isn't quite `CLOCK_BOOTTIME`
* either; however it is fast and almost always goes in one direction.
*
* Intel architecture guarantees that a mapping exists between rdtsc &
* nanoseconds only if the cpu advertises invariant timestamps support
* however this shouldn't matter for a monotonic clock since we really
* don't want to have it tick while suspended. Sadly that shall happen
* since nearly all x86 microprocessors support invariant tsc which is
* why we try to avoid this fallback when possible.
*/
int sys_sysctl(int *, unsigned, void *, size_t *, void *, size_t) libcesque;
static struct {
atomic_uint once;
unsigned long base;
struct timespec boot;
} g_mono;
static struct timespec get_boot_time_xnu(void) {
struct timeval t;
size_t n = sizeof(t);
int mib[] = {1 /* CTL_KERN */, 21 /* KERN_BOOTTIME */};
if (sys_sysctl(mib, 2, &t, &n, 0, 0) == -1)
__builtin_trap();
return timeval_totimespec(t);
}
static void sys_clock_gettime_mono_init(void) {
g_mono.base = rdtsc();
if (IsXnu()) {
g_mono.boot = get_boot_time_xnu();
} else {
__builtin_trap();
}
}
int sys_clock_gettime_mono(struct timespec *time) {
uint64_t nanos;
uint64_t cycles;
cosmo_once(&g_mono.once, sys_clock_gettime_mono_init);
// ensure we get the full 64 bits of counting, which avoids wraparound
cycles = rdtsc() - g_mono.base;
// this is a crude approximation, that's worked reasonably well so far
// only the kernel knows the actual mapping between rdtsc and nanosecs
// which we could attempt to measure ourselves using clock_gettime but
// we'd need to impose 100 ms of startup latency for a guess this good
nanos = cycles / 3;
*time = timespec_add(g_mono.boot, timespec_fromnanos(nanos));
return 0;
}