netbsd man page for _lwp_ctl

_LWP_CTL(2)						      BSD System Calls Manual						       _LWP_CTL(2)

NAME
     _lwp_ctl -- prepare per-LWP communication area between kernel and userland

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <lwp.h>

     int
     _lwp_ctl(int features, struct lwpctl **address);

DESCRIPTION
     _lwp_ctl() prepares per-LWP communication area for the calling LWP, and maps it into the calling process' address space.  It takes the fol-
     lowing arguments.

     features  The bitwise-OR of the following flags.

	       LWPCTL_FEATURE_CURCPU  Request lc_curcpu.

	       LWPCTL_FEATURE_PCTR    Request lc_pctr.

     address   The address to store a pointer to lwpctl structure for the calling LWP.

     The per-LWP communication area is described by an lwpctl structure.  It has following members, depending on features.

     int lc_curcpu  The integral identifier of the CPU on which the LWP is running, or LWPCTL_CPU_NONE when the LWP is not running on any CPU.
		    It's updated by the kernel and should be considered as read-only for userland.  It's available only if requested with the
		    LWPCTL_FEATURE_CURCPU flag.

     int lc_pctr    The integer which is incremented on every context switches to the LWP.  It can be used to detect preemption of the LWP.  (thus
		    its name "preemption counter".)  It's updated by the kernel and should be considered as read-only for userland.  It's avail-
		    able only if requested with the LWPCTL_FEATURE_PCTR flag.

RETURN VALUES
     _lwp_ctl() returns 0 on success.  Otherwise, -1 is returned and errno is set to indicate the error.

SEE ALSO
     errno(2)

BSD
								    May 5, 2008 							       BSD