_LWP_CREATE(2) System Calls Manual _LWP_CREATE(2)

_lwp_create — create a new light-weight process

Standard C Library (libc, -lc)

#include <lwp.h>

int
_lwp_create(ucontext_t *context, unsigned long flags, lwpid_t *new_lwp);

() causes creation of a new light-weight process, or LWP, and adds it to the current process. The context argument specifies the initial execution context for the new LWP including signal mask, stack, and machine registers. The signal stack of the newly created light-weight process is reset to disabled. If this context specifies invalid register values (for example privilege escalation by setting machine dependent bits forbidden for user processes), or does not specify cpu register values (uc_flags does not have the _UC_CPU bit set), the call will fail and errno will be set to EINVAL.

The following flags affect the creation of the new LWP:

The LWP is created detached. The resources associated with a detached LWP will be automatically reclaimed by the system when the LWP exits. Otherwise, a terminated LWP's resources will not be reclaimed until its status is reported to another LWP via _lwp_wait(2).
The LWP is created suspended, and will not begin execution until it is resumed by another LWP via _lwp_continue(2).

The LWP ID of the new LWP is stored in the location pointed to by new_lwp.

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

_lwp_create() will fail and no LWP will be created if:

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The system-imposed limit on the total number of LWPs under execution would be exceeded. This limit is configuration-dependent.
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The address pointed to by context or new_lwp is outside the process's allocated address space.
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The ucontext_t passed is invalid.
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There is insufficient swap space for the new LWP.

_lwp_continue(2), _lwp_exit(2), _lwp_wait(2), _lwp_makecontext(3)

The _lwp_create() system call first appeared in NetBSD 2.0.

April 21, 2017 NetBSD 11.0