75 lines
2 KiB
Groff
75 lines
2 KiB
Groff
.TH MAKECONTEXT 3 "Mar 2, 2010"
|
|
.SH NAME
|
|
makecontext, swapcontext \- manipulate user contexts
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.ft B
|
|
#include <ucontext.h>
|
|
|
|
void makecontext(ucontext\_t *\fIucp\fP, void \fI(*func)(void)\fP, int \fIargc\fP, ...)
|
|
int swapcontext(ucontext\_t *\fIoucp\fP, const ucontext\_t *\fIucp\fP)
|
|
.SH DESCRIPTION
|
|
The
|
|
.BR makecontext (3)
|
|
,
|
|
.BR swapcontext (3)
|
|
,
|
|
.BR getcontext (3)
|
|
, and
|
|
.BR setcontext (3)
|
|
together form a set of functions that allow user-level context switching between multiple threads of control within a process.
|
|
.PP
|
|
The
|
|
.BR makecontext ()
|
|
function modifies the user thread pointed to by
|
|
.I ucp
|
|
to continue execution by invoking function
|
|
.I func
|
|
and passing that function a number of
|
|
.I argc
|
|
integer arguments. The value of
|
|
.I argc
|
|
must match the number of integer arguments passed to
|
|
.I func
|
|
, otherwise the behavior is undefined. Context
|
|
.I ucp
|
|
must have been initialized by a call to
|
|
.BR getcontext (3)
|
|
and have a stack allocated for it. The address of the stack must be assigned to \fIucp\->uc_stack.ss_sp\fP and the size of the stack to \fIucp\->uc_stack.ss_size\fP. The \fIucp\->uc_link\fP member is used to determine which successor context is run after the context modified by
|
|
.BR makecontext ()
|
|
returns. If left NULL, the process exits.
|
|
.PP
|
|
The
|
|
.BR swapcontext ()
|
|
function saves the current context in the context structure pointed to by
|
|
.I oucp
|
|
and sets the context to the context structure pointed to by \fIucp\fP.
|
|
|
|
.SH "RETURN VALUE"
|
|
When successful,
|
|
.BR swapcontext ()
|
|
returns 0. Otherwise, -1 is returned and
|
|
.I errno
|
|
is set to indicate the error. Note that a successful call to
|
|
.BR swapcontext ()
|
|
actually does not return. Only after returning to the context that called
|
|
.BR swapcontext ()
|
|
, it appears as if
|
|
.BR swapcontext ()
|
|
returned 0.
|
|
|
|
.SH "ERRORS"
|
|
.TP 15
|
|
[EFAULT]
|
|
Either the \fIucp\fP or \fIoucp\fP is a NULL pointer.
|
|
.TP 15
|
|
[EINVAL]
|
|
The context is not properly initialized.
|
|
.TP 15
|
|
[ENOMEM]
|
|
The \fIucp\fP argument does not have enough stack left to complete the operation.
|
|
.SH "SEE ALSO"
|
|
.BR getcontext (3).
|
|
|
|
.SH "AUTHORS"
|
|
Thomas Veerman
|