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_LWP_CTL(2)                   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 <sys/lwpctl.h>
     #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 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 available only if requested with the
                   LWPCTL_FEATURE_PCTR flag.

RETURN VALUES
     The _lwp_ctl() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

SEE ALSO
     errno(2)

NetBSD 10.99                    April 13, 2012                    NetBSD 10.99