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_LWP_CTL(2) BSD System Calls Manual _LWP_CTL(2)
_lwp_ctl -- prepare per-LWP communication area between kernel and userland
Standard C Library (libc, -lc)
_lwp_ctl(int features, struct lwpctl **address);
_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
_lwp_ctl() returns 0 on success. Otherwise, -1 is returned and errno is set to indicate the
BSD May 5, 2008 BSD
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