Date: Wed, 4 Jun 2003 11:35:31 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Jeff Roberson <jroberson@chesapeake.net> Cc: freebsd-threads@freebsd.org Subject: Re: FreeBSD pthread_equal "bug" Message-ID: <Pine.BSF.4.21.0306041129130.2846-100000@InterJet.elischer.org> In-Reply-To: <20030604130858.M69975-100000@mail.chesapeake.net>
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On Wed, 4 Jun 2003, Jeff Roberson wrote: > On 4 Jun 2003, Kern Sibbald wrote: > > > > > I'm not sure what the POSIX specification says, > > if I were programming it, I would not be content > > with the FreeBSD current implementation especially > > considering that both Solaris and Linux do it "correctly". > > Would you rather your application failed immediately, or in a subtle, > unexpected way after many hours/weeks/months of run time? Dan says the > standard allows for immediate reuse. If that is correct, then Solaris, > linux, and FreeBSD all do it correctly for the only definition of > correctly that matters. > > Simply adding an ID is problematic because the ids will wrap. Without > using some deterministic notification you can't be sure that it isn't an > expired thread. I will quote from "Programming with Posix threads" by David R Butenhof.. He is one o fthe main authors of the Posix threads standard so I tend to treat this book as a guide.. "Once a thread is recycled, the thread's ID (pthread_t) is no longer valid. You cannot join with the thread, canel it, or anything else. The terminated thread's ID (which may be the addess of a system data structure) may be assigned to a new thread. Instead of receiving an ESRCH failure from your call to pthread_cancel, you would instead cancel a different thread." I think that is pretty explicit as far as expected bahaviour. HAVING SAID THAT, it is not impossible that at some time in the future we may use some other pthread_t type, e.g an incrementing TID, but at this time I think we are well within the standard... Julian
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