Date: Tue, 18 Dec 2001 16:01:44 -0800 (PST) From: Julian Elischer <julian@elischer.org> To: current@freebsd.org Subject: Is this a bug in the fork() code? Message-ID: <Pine.BSF.4.21.0112181553140.36281-100000@InterJet.elischer.org>
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Near the end of fork1():
/*
* If RFSTOPPED not requested, make child runnable and add to
* run queue.
*/
microtime(&(p2->p_stats->p_start));
p2->p_acflag = AFORK;
if ((flags & RFSTOPPED) == 0) {
mtx_lock_spin(&sched_lock);
p2->p_stat = SRUN; /* XXXKSE */
setrunqueue(td2);
mtx_unlock_spin(&sched_lock);
}
note that it may have made itself only a child of init.....
later at the very end of fork1():
/*
* Return child proc pointer to parent.
*/
*procp = p2;
return (0);
}
now, what is to say that the process has not exitted by this stage, and
been reeped by init (on SMP)
particularly since between the two is:
/*
* 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).
*/
PROC_LOCK(p2);
while (p2->p_flag & P_PPWAIT)
msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0);
PROC_UNLOCK(p2);
It may be that due to some semantics of teh fork calls
you cannot have P_PPWAIT and a process queued to run on the other
processor while reparented to init(1) but I can't see it..
the result would be that the return value MIGHT be teh pid
of a totally different process if the proc structure had been re-used.
Alternatively I could have some good weed here...
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