IABSD.fr/src/lib/libc/thread/synch.h

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• Author : pirofti
  Date : 2020-07-06 13:33:05
  Hash : d82e6535
  Message : Add support for timeconting in userland. This diff exposes parts of clock_gettime(2) and gettimeofday(2) to userland via libc eliberating processes from the need for a context switch everytime they want to count the passage of time. If a timecounter clock can be exposed to userland than it needs to set its tc_user member to a non-zero value. Tested with one or multiple counters per architecture. The timing data is shared through a pointer found in the new ELF auxiliary vector AUX_openbsd_timekeep containing timehands information that is frequently updated by the kernel. Timing differences between the last kernel update and the current time are adjusted in userland by the tc_get_timecount() function inside the MD usertc.c file. This permits a much more responsive environment, quite visible in browsers, office programs and gaming (apparently one is are able to fly in Minecraft now). Tested by robert@, sthen@, naddy@, kmos@, phessler@, and many others! OK from at least kettenis@, cheloha@, naddy@, sthen@

• lib/libc/thread/synch.h

• /*	$OpenBSD: synch.h,v 1.5 2020/07/06 13:33:06 pirofti Exp $ */
  /*
   * Copyright (c) 2017 Martin Pieuchot
   *
   * Permission to use, copy, modify, and 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 <sys/atomic.h>
  #include <sys/time.h>
  #include <sys/futex.h>
  
  static inline int
  _wake(volatile uint32_t *p, int n)
  {
  	return futex(p, FUTEX_WAKE_PRIVATE, n, NULL, NULL);
  }
  
  static inline int
  _twait(volatile uint32_t *p, int val, clockid_t clockid, const struct timespec *abs)
  {
  	struct timespec rel;
  
  	if (abs == NULL)
  		return futex(p, FUTEX_WAIT_PRIVATE, val, NULL, NULL);
  
  	if (abs->tv_nsec >= 1000000000 || WRAP(clock_gettime)(clockid, &rel))
  		return (EINVAL);
  
  	rel.tv_sec = abs->tv_sec - rel.tv_sec;
  	if ((rel.tv_nsec = abs->tv_nsec - rel.tv_nsec) < 0) {
  		rel.tv_sec--;
  		rel.tv_nsec += 1000000000;
  	}
  	if (rel.tv_sec < 0)
  		return (ETIMEDOUT);
  
  	return futex(p, FUTEX_WAIT_PRIVATE, val, &rel, NULL);
  }
  
  static inline int
  _requeue(volatile uint32_t *p, int n, int m, volatile uint32_t *q)
  {
  	return futex(p, FUTEX_REQUEUE_PRIVATE, n, (void *)(long)m, q);
  }