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New vfork(2) implementation, whith semantics matching those of the original

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3BSD vfork(2), i.e. share address space w/ parent and block parent.

Keep statistics on the total number of forks, the number of forks that
block the parent, and the number of forks that share the address space
with the parent.
This commit is contained in:
thorpej 1998-01-04 03:52:02 +00:00
parent 43677af399
commit 740f872797
1 changed files with 36 additions and 9 deletions
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45
sys/kern/kern_fork.c
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@ -1,4 +1,4 @@
/* $NetBSD: kern_fork.c,v 1.33 1998/01/03 02:49:30 thorpej Exp $ */
/* $NetBSD: kern_fork.c,v 1.34 1998/01/04 03:52:02 thorpej Exp $ */
/*
* Copyright (c) 1982, 1986, 1989, 1991, 1993
@ -53,6 +53,7 @@
#include <sys/file.h>
#include <sys/acct.h>
#include <sys/ktrace.h>
#include <sys/vmmeter.h>
#include <sys/syscallargs.h>
@ -60,8 +61,6 @@
int nprocs = 1; /* process 0 */
int fork1 __P((struct proc *, int, register_t *));
/*ARGSUSED*/
int
sys_fork(p, v, retval)
@ -73,6 +72,10 @@ sys_fork(p, v, retval)
return (fork1(p, 0, retval));
}
/*
* vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM).
* Address space is not shared, but parent is blocked until child exit.
*/
/*ARGSUSED*/
int
sys_vfork(p, v, retval)
@ -81,13 +84,28 @@ sys_vfork(p, v, retval)
register_t *retval;
{
return (fork1(p, 1, retval));
return (fork1(p, FORK_PPWAIT, retval));
}
/*
* New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2)
* semantics. Address space is shared, and parent is blocked until child exit.
*/
/*ARGSUSED*/
int
sys___vfork14(p, v, retval)
struct proc *p;
void *v;
register_t *retval;
{
return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval));
}
int
fork1(p1, isvfork, retval)
fork1(p1, flags, retval)
register struct proc *p1;
int isvfork;
int flags;
register_t *retval;
{
register struct proc *p2;
@ -222,7 +240,7 @@ again:
if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
if (isvfork)
if (flags & FORK_PPWAIT)
p2->p_flag |= P_PPWAIT;
LIST_INSERT_AFTER(p1, p2, p_pglist);
p2->p_pptr = p1;
@ -251,7 +269,7 @@ again:
* Finish creating the child process. It will return through a
* different path later.
*/
vm_fork(p1, p2, FALSE);
vm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE);
/*
* Make child runnable, set start time, and add to run queue.
@ -268,12 +286,21 @@ again:
*/
PRELE(p1);
/*
* Update stats now that we know the fork was successful.
*/
cnt.v_forks++;
if (flags & FORK_PPWAIT)
cnt.v_forks_ppwait++;
if (flags & FORK_SHAREVM)
cnt.v_forks_sharevm++;
/*
* Preserve synchronization semantics of vfork. If waiting for
* child to exec or exit, set P_PPWAIT on child, and sleep on our
* proc (in case of exit).
*/
if (isvfork)
if (flags & FORK_PPWAIT)
while (p2->p_flag & P_PPWAIT)
tsleep(p1, PWAIT, "ppwait", 0);