Date: Thu, 30 Jan 1997 16:45:10 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: cracauer@wavehh.hanse.de Cc: rminnich@Sarnoff.COM, freebsd-hackers@FreeBSD.ORG Subject: Re: Using rfork() / threads Message-ID: <199701302345.QAA00636@phaeton.artisoft.com> In-Reply-To: <9701301753.AA23376@wavehh.hanse.de> from "Martin Cracauer" at Jan 30, 97 06:53:18 pm
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> >VM space handling is a little different. If you request VM space sharing, > >you don't exactly get Vm address space sharing: what you get is instead > >shared data areas where in normal fork they are copied. More details on > >request. The effect is what you want, though: shared data areas. > > Could you explain a bit more. What exactly is the difference between > VM space sharing and shared data areas from the process' and the > kernel perspective? The per process open file table points to the same location, for one (that's actually a biggie). If I open a file in one process, it is open for both processes. If I close it, it's closed. There is one fd offset associated with the object -- if one process writes it, the offset is advanced, and if the other writes it, it's advanced again. There is a potential race as to who gets to do the write. Etc. Regards, Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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