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dd8544c3bd
The worst issue I had with consts.sh for clock_gettime is how it defined too many clocks. So I looked into these clocks all day to figure out how how they overlap in functionality. I discovered counter-intuitive things such as how CLOCK_MONOTONIC should be CLOCK_UPTIME on MacOS and BSD, and that CLOCK_BOOTTIME should be CLOCK_MONOTONIC on MacOS / BSD. Windows 10 also has some incredible new APIs, that let us simplify clock_gettime(). - Linux CLOCK_REALTIME -> GetSystemTimePreciseAsFileTime() - Linux CLOCK_MONOTONIC -> QueryUnbiasedInterruptTimePrecise() - Linux CLOCK_MONOTONIC_RAW -> QueryUnbiasedInterruptTimePrecise() - Linux CLOCK_REALTIME_COARSE -> GetSystemTimeAsFileTime() - Linux CLOCK_MONOTONIC_COARSE -> QueryUnbiasedInterruptTime() - Linux CLOCK_BOOTTIME -> QueryInterruptTimePrecise() Documentation on the clock crew has been added to clock_gettime() in the docstring and in redbean's documentation too. You can read that to learn interesting facts about eight essential clocks that survived this purge. This is original research you will not find on Google, OpenAI, or Claude I've tested this change by porting *NSYNC to become fully clock agnostic since it has extensive tests for spotting irregularities in time. I have also included these tests in the default build so they no longer need to be run manually. Both CLOCK_REALTIME and CLOCK_MONOTONIC are good across the entire amd64 and arm64 test fleets.
100 lines
5.1 KiB
C
100 lines
5.1 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/struct/timespec.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/sysv/consts/clock.h"
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#include "libc/sysv/consts/timer.h"
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/**
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* Sleeps for particular amount of time.
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*
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* Here's how you could sleep for one second:
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*
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* clock_nanosleep(0, 0, &(struct timespec){1}, 0);
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*
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* Your sleep will be interrupted automatically if you do something like
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* press ctrl-c during the wait. That's an `EINTR` error and it lets you
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* immediately react to status changes. This is always the case, even if
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* you're using `SA_RESTART` since this is a `@norestart` system call.
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*
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* void OnCtrlC(int sig) {} // EINTR only happens after delivery
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* signal(SIGINT, OnCtrlC); // do delivery rather than kill proc
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* printf("save me from sleeping forever by pressing ctrl-c\n");
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* clock_nanosleep(0, 0, &(struct timespec){INT_MAX}, 0);
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* printf("you're my hero\n");
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*
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* If you want to perform an uninterruptible sleep without having to use
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* sigprocmask() to block all signals then this function provides a good
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* solution to that problem. For example:
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*
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* struct timespec rel, now, abs;
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* clock_gettime(CLOCK_REALTIME, &now);
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* rel = timespec_frommillis(100);
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* abs = timespec_add(now, rel);
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* while (clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &abs, 0));
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*
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* will accurately spin on `EINTR` errors. That way you're not impeding
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* signal delivery and you're not loosing precision on the wait timeout.
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* This function has first-class support on Linux, FreeBSD, and NetBSD;
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* on OpenBSD it's good; on XNU it's bad; and on Windows it's ugly.
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*
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* @param clock may be
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* - `CLOCK_REALTIME`
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* - `CLOCK_MONOTONIC`
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* @param flags can be 0 for relative and `TIMER_ABSTIME` for absolute
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* @param req can be a relative or absolute time, depending on `flags`
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* @param rem shall be updated with the remainder of unslept time when
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* (1) it's non-null; (2) `flags` is 0; and (3) -1 w/ `EINTR` is
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* returned; if this function returns 0 then `rem` is undefined;
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* if flags is `TIMER_ABSTIME` then `rem` is ignored
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* @return 0 on success, or errno on error
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* @raise EINTR when a signal got delivered while we were waiting
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* @raise ECANCELED if thread was cancelled in masked mode
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* @raise ENOTSUP if `clock` is known but we can't use it here
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* @raise EFAULT if `req` or null or bad memory was passed
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* @raise EINVAL if `clock` is unknown to current platform
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* @raise EINVAL if `flags` has an unrecognized value
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* @raise EINVAL if `req->tv_nsec ∉ [0,1000000000)`
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* @raise ENOSYS on bare metal
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* @cancelationpoint
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* @returnserrno
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* @norestart
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*/
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errno_t clock_nanosleep(int clock, int flags, //
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const struct timespec *req, //
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struct timespec *rem) {
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if (IsMetal())
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return ENOSYS;
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if (IsLinux() && clock == CLOCK_REALTIME_COARSE)
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clock = CLOCK_REALTIME;
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if (IsLinux() && clock == CLOCK_MONOTONIC_COARSE)
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clock = CLOCK_MONOTONIC;
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if (clock == 127 || //
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(flags & ~TIMER_ABSTIME) || //
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req->tv_sec < 0 || //
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!(0 <= req->tv_nsec && req->tv_nsec <= 999999999))
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return EINVAL;
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int rc;
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errno_t err, old = errno;
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rc = sys_clock_nanosleep(clock, flags, req, rem);
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err = !rc ? 0 : errno;
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errno = old;
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return err;
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}
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