_LWP_PARK(2) BSD System Calls Manual _LWP_PARK(2)NAME_lwp_park — wait interruptably in the kernel
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <lwp.h>
int
_lwp_park(const struct timespec *abstime, lwpid_t unpark,
const void *hint, const void *unparkhint);
DESCRIPTION_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:
· The abstime argument is non-NULL, and the absolute UTC time it speci‐
fies has passed.
· The LWP receives a directed signal posted using _lwp_kill(), or is
elected to handle a signal on behalf of its containing process.
· The LWP is awoken by another LWP in the same process that has made a
call to _lwp_wakeup().
· The LWP is awoken by another LWP in the same process that has made a
call to _lwp_unpark() or _lwp_unpark_all().
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);
RETURN VALUES_lwp_park() may return a value of 0. Otherwise, -1 is returned and errno
is set to provide more information.
ERRORS
[EALREADY]
A request was made to wake the LWP before it began to wait in
the kernel.
[EINTR] The LWP has been awoken by a signal or by a call to one of the
following functions: _lwp_unpark(), _lwp_unpark_all(),
_lwp_wakeup().
[EINVAL] The time value specified by abstime is invalid.
[ESRCH] No LWP can be found in the current process corresponding to
unpark.
[ETIMEDOUT]
The UTC time specified by abstime has passed.
SEE ALSO_lwp_unpark(2), _lwp_unpark_all(2), _lwp_wakeup(2)HISTORY
The _lwp_park() system call first appeared in NetBSD 5.0.
BSD September 25, 2007 BSD
