Date: Wed, 20 Feb 2002 17:27:48 -0500 (EST) From: John Baldwin <jhb@FreeBSD.org> To: Terry Lambert <tlambert2@mindspring.com> Cc: current@FreeBSD.ORG, Peter Wemm <peter@wemm.org>, Matthew Dillon <dillon@apollo.backplane.com>, Julian Elischer <julian@elischer.org> Subject: Re: Patch sets to date and timing tests with Giant out of userre Message-ID: <XFMail.020220172748.jhb@FreeBSD.org> In-Reply-To: <3C720859.C77590F0@mindspring.com>
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On 19-Feb-02 Terry Lambert wrote: > Julian Elischer wrote: >> The fully safe version of this code is: >> td->td_retval[0] = td->td_ucred->cr_ruid; >> td->td_retval[1] = td->td_ucred->cr_uid; >> return (0); >> >> because td->td_ucred is read-only for it's whole existance. > > ??? > > Are you sure that td->td_ucred can't change in the middle, > to point to a different ucred, as a result of kernel > preemption? Yes. A thread's ucred pointer is constant teh entire time that it is in the kernel. If we get preempted who cares. We will still be teh same thread when we continue executing. :) -- 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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