CLONE3(2) System Programmer's Manual CLONE3(2)
NAME
clone3 - create a child process
SYNOPSIS
#include <clone.h>
int clone3(pid_t parent, pid_t co_parent,
int (*fn)(void *), void *child_stack,
int flags, void *arg, ... );
DESCRIPTION
clone3() creates a new process, in a manner similar to fork(2).
Unlike fork(2), these calls allow the child process to share parts of
its execution context with the parent and co-parent processes,
such as their home, food, and approximately half of their genetic
material.
The main use of clone3() is to implement offspring: sentient beings
that run concurrently with the parents in a shared environment.
When the child process is created with clone3(), it executes the
function application fn(arg). (This differs from fork(2), where
execution continues in the child from the point of the fork(2) call.)
The fn argument is a pointer to a function that is called by the child
process at the beginning of its execution. The arg argument is passed
to the fn function. Although the parent processes may supply a suitable
fn function, the child process has a mind of its own and may deviate
from its execution at will.
Executing clone3 will randomly select half of the genes from each
parent, resulting in a selection of phenotypes according to
Mendelian inheritance. By design this process increases the
number of bits in the global entropy pool, making recovery of the
random state impractical.
The child_stack argument specifies the location of the pile of
diapers used by the child process. After the child process leaves
the EMBRYO state and until it acquires the CAP_POTTY capability,
it may frequently dump core. The calling process must therefore
set up a large store of waste disposal units and pass a pointer to
this store to clone3(). After a successful core dump it is necessary
for a parent to handle the condition as soon as possible.
The flags parameter may be bitwise-or'ed with zero or more of the
following constants, in order to specify the behavior of the system
call:
CLONE_XY
Setting CLONE_XY indicates to the system that a child of the
male gender is requested. This is only a hint to the system
and may not be honored.
CLONE_XX
Setting CLONE_XX indicates to the system that a child of the
female gender is requested. This is only a hint to the system
and may not be honored.
If both CLONE_XY and CLONE_XX are set, results are undefined.
RETURN VALUE
On completion, the thread ID of the child process is returned in
both parents' thread of execution. During execution, the child process
may signal an error condition by raising any of the following signals.
SIGNALS
HUNGRY The stomach monitor process has detected an empty condition.
The parent may correct the condition by supplying food.
TIRED The process has executed too many cycles and must enter
sleep(3).
GRUMPY The process is raising signals at full volume for unknown
reasons. The parent process should attach pacifier(2) to
the child process and attempt to cause it to enter sleep(3).
HAPPY The process is in a suitable state for taking pictures for
grandparents.
CONFORMING TO
Biology 101.
BUGS
Child process may spit-up on your new shirt; a burping cloth is
recommended.
EXAMPLE
The following psuedo-code illustrates the intended usage:
#include <clone.h>
int main(int argc, char *argv[])
{
pid_t ange = /* ... */
pid_t bob = /* ... */
pid_t alex;
alex = clone3(ange, bob, fn, stack, CLONE_XY, NULL);
sleep(86400 * 30 * 9);
take_snapshot(alex);
}
This yields the following:
Alexander Yit-Keung Copeland
Born 26 June, 2010
Weight 7 lbs 12 oz
SEE ALSO
fork(2), futex(2), getpid(2), gettid(2), set_thread_area(2),
set_tid_address(2), tkill(2), unshare(2), wait(2), capabilities(7),
pthreads(7)
CLONE3(2) 2010-06-26 CLONE3(2)
Last night I had the pleasure of driving my car less than a mile from the nearby metro to our apartment, during a heavy snow, in rush hour. Normally I walk, but this area is bad about keeping sidewalks clear in snowy weather, so driving is sometimes the safer option. It took me an hour and a half to cover the distance, at a blazing average speed of 2/3 mph.
