| _LWP_PARK(2) | System Calls Manual | _LWP_PARK(2) | 
_lwp_park —
#include <lwp.h>
int
  
  _lwp_park(clockid_t
    clock_id, int
    flags, struct timespec
    *ts, lwpid_t
    unpark, const void
    *hint, const void
    *unparkhint);
_lwp_park() can be used to synchronize access to
  resources among multiple light-weight processes. It causes the calling LWP to
  wait interruptably in the kernel, until one of the following conditions is
  met:
NULL,
      and the time it specifies has passed. The ts time
      can be an relative interval to wait if the flags
      argument does not contain TIMER_ABSTIME or it can
      be an absolute time. The clock_id argument contains
      the clock to be used; it can be: CLOCK_REALTIME or
      CLOCK_MONOTONIC._lwp_kill(), or is elected to handle a signal on
      behalf of its containing process._lwp_wakeup()._lwp_unpark() or
      _lwp_unpark_all().If the ts argument contains a relative time
    interval, it will be modified to contain the remaining time to sleep when
    _lwp_park() returns.
The preferred method to awaken an LWP sleeping as a result of a
    call to _lwp_park() is to make a call to
    _lwp_unpark(), or
    _lwp_unpark_all(). The
    _lwp_wakeup() system call is a more general
    facility, and requires more resources to execute.
The optional hint argument specifies the
    address of object upon which the LWP is synchronizing. When the
    hint value is matched between calls to
    _lwp_park() and
    _lwp_unpark() or
    _lwp_unpark_all(), it may reduce the time necessary
    for the system to resume execution of waiting LWPs.
The unpark and unparkhint arguments can be used to fold a park operation and unpark operation into a single system call. If unpark is non-zero, the system will behave as if the following call had been made before the calling thread begins to wait:
_lwp_unpark(unpark, unparkhint);
_lwp_park() may return a value of 0. Otherwise, -1 is
  returned and errno is set to provide more information.
EALREADY]EINTR]_lwp_unpark(),
      _lwp_unpark_all(),
      _lwp_wakeup().EINVAL]ESRCH]ETIMEDOUT]_lwp_park() system call first appeared in
  NetBSD 5.0.
| December 7, 2017 | NetBSD 9.4 |