Date: Sun, 17 Aug 2003 15:06:23 -0700
From: Marcel Moolenaar <marcel@xcllnt.net>
To: Daniel Eischen <eischen@vigrid.com>
Cc: threads@freebsd.org
Subject: Re: First draft: rewrite of {get|set|swap}context(3)
Message-ID: <20030817220623.GA1661@dhcp42.pn.xcllnt.net>
In-Reply-To: <Pine.GSO.4.10.10308171657400.11196-100000@pcnet5.pcnet.com>
References: <20030817185015.GB928@dhcp42.pn.xcllnt.net> <Pine.GSO.4.10.10308171657400.11196-100000@pcnet5.pcnet.com>
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On Sun, Aug 17, 2003 at 05:12:29PM -0400, Daniel Eischen wrote: > On Sun, 17 Aug 2003, Marcel Moolenaar wrote: > > > Please review the attached patch and let me know to what extend it > > introduces breakages. It is the result of "aggressive engineering" > > to provoke comments and further fuel discussion. The reason for this > > approach is that we currently do not initialize any fields other than > > the mcontext and sigmask and only partially copyin() and copyout() > > the contexts (typically only the mcontext and sigmask fields). This > > generally is very sensitive to breakages, especially when we intro- > > duce flags or need to use any of the spare fields. > > > > getcontext(3): the whole ucontext is zeroed before (partially) filled > > and we copyout() all of it. This means that uc_link can only > > be set/defined after calling setcontext(). > > This prevents reuse of the same context without resetting > uc_link after every usage. I don't see any requirement > by POSIX that uc_link be left intact after getcontext(), > but it might be worth preserving... It's up to you. Yes, it's a tricky issue. I'll begin runtime testing and think about it some more. I don't want to rush it... BTW: I think we need to preserve uc_stack as well. -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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