Date: Tue, 18 Dec 2001 16:40:42 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Alfred Perlstein <bright@mu.org> Cc: current@freebsd.org, Julian Elischer <julian@elischer.org> Subject: Re: Is this a bug in the fork() code? Message-ID: <XFMail.011218164042.jhb@FreeBSD.org> In-Reply-To: <20011218182421.M59831@elvis.mu.org>
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On 19-Dec-01 Alfred Perlstein wrote: > * Julian Elischer <julian@elischer.org> [011218 18:20] wrote: >> >> 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... > > That's not possible, since the parent is waiting the kernel will > not reparent unless the parent exits, which it doesn't because it's > waiting for the child. > > You owe the Oracle a large bong rip. Look at RFNOWAIT silly. It forces a parent to init during fork1() itself. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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