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NetBSD 6.1.5 - man page for _lwp_ctl (netbsd section 2)

_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 following 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 mem-
     bers, 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 available 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


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