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NAME

_lwp_create − create a new light-weight process

SYNOPSIS

#include <sys/lwp.h>

int _lwp_create(ucontext_t *contextp, uint_t flags, lwpid_t *new_lwp);

The _lwp_create() function adds a lightweight process (LWP) to the current process. The contextp argument specifies the initial signal mask, stack, and machine context (including the program counter and stack pointer) for the new LWP. The new LWP inherits the scheduling class and priority of the caller.

If _lwp_create() is successful and new_lwp is not NULL, the ID of the new LWP is stored in the location pointed to by new_lwp.

The flags argument specifies additional attributes for the new LWP. The value in flags is constructed by the bitwise inclusive OR operation of the following values:
LWP_DETACHED

The LWP is created detached.

LWP_DAEMON

The LWP is created as a daemon LWP.

LWP_SUSPENDED

The LWP is created suspended.

If LWP_DETACHED or LWP_DAEMON is specified, then the LWP is created in the detached state. Otherwise the LWP is created in the undetached state. The ID (and system resources) associated with a detached LWP can be automatically reclaimed when the LWP exits. The ID of an undetached LWP cannot be reclaimed until it exits and another LWP has reported its termination by way of _lwp_wait(2). This allows the waiting LWP to determine that the waited for LWP has terminated and to reclaim any process resources that it was using.

If LWP_DAEMON is specified, then in addition to being created in the detached state, the LWP is created as a daemon LWP. Daemon LWPs do not interfere with the exit conditions for a process. A process will exit as though _exit(0) had been called when the last non-daemon LWP calls _lwp_exit() (see exit(2) and _lwp_exit(2)). Also, an LWP that is waiting in _lwp_wait(2) for any LWP to terminate will return EDEADLK when all remaining LWPs in the process are either daemon LWPs or other LWPs waiting in _lwp_wait().

If LWP_SUSPENDED is specified, then the LWP is created in a suspended state. This allows the creator to change the LWP’s inherited attributes before it starts to execute. The suspended LWP can only be resumed by way of _lwp_continue(2). If LWP_SUSPENDED is not specified the LWP can begin to run immediately after it has been created.

RETURN VALUES

Upon successful completion, 0 is returned. A non-zero value indicates an error.

ERRORS

If any of the following conditions are detected, _lwp_create() fails and returns the corresponding value:
EFAULT

Either the context parameter or the new_lwp parameter point to invalid addresses.

EAGAIN

A system limit is exceeded, (for example, too many LWPs were created for this real user ID).

EINVAL

The flags argument contains values other than those specified above.

EXAMPLES

Example 1: How a stack is allocated to a new LWP.

This example shows how a stack is allocated to a new LWP. The _lwp_makecontext() function is used to set up the context parameter so that the new LWP begins executing a function.

contextp = (ucontext_t *)malloc(sizeof(ucontext_t));
stackbase = malloc(stacksize);
_lwp_makecontext(contextp, func, arg, private, stackbase, stacksize);
sigprocmask(SIGSETMASK, NULL, &contextp->uc_sigmask);
error = _lwp_create(contextp, NULL, &new_lwp);

USAGE

Applications should use bound threads rather than the _lwp_* functions (see thr_create(3THR)). Using LWPs directly is not advised because libraries are only safe to use with threads, not LWPs.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

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