Originální popis anglicky:
makecontext, swapcontext - manipulate user context
Návod, kniha: Linux Programmer's Manual
#include <ucontext.h>
void makecontext(ucontext_t *ucp, void
*func(), int argc, ...);
int swapcontext (ucontext_t *oucp, ucontext_t
*ucp);
In a SysV-like environment, one has the type
ucontext_t defined in
<ucontext.h> and the four functions
getcontext(),
setcontext(),
makecontext() and
swapcontext() that allow
user-level context switching between multiple threads of control within a
process.
For the type and the first two functions, see
getcontext(2).
The
makecontext() function modifies the context pointed to by
ucp
(which was obtained from a call to
getcontext()). Before calling
makecontext(), one should allocate a new stack for this context,
assigning to
ucp->uc_stack, and define a successor context,
assigning to
ucp->uc_link. When this context is later activated
(using
setcontext() or
swapcontext()) then first the function
func is called, with the arguments specified following
argc
(where
argc must contain the number of these arguments), and when this
function returns, the successor context is activated. When the successor
context pointer is NULL, the thread exits.
The
swapcontext() function saves the current context in the structure
pointed to by
oucp, and then activates the context pointed to by
ucp.
When successful,
makecontext() returns 0 and
swapcontext() does
not return. (But we may return later, in case
oucp is activated, in
which case it looks like
swapcontext() returns 0.) On error, both
return -1 and set
errno appropriately.
- ENOMEM
- Insufficient stack space left.
The interpretation of
ucp->uc_stack is just as in
sigaltstack(2), namely, this struct contains start and length of a
memory area to be used as stack, regardless of the direction of growth of the
stack. So, it is not necessary for the user program to worry about this
direction.
SUSv2, POSIX 1003.1-2001.
getcontext(2),
sigaction(2),
sigaltstack(2),
sigprocmask(2),
sigsetjmp(3)
