Date: Sat, 7 Oct 2000 13:27:52 +0930 From: Greg Lehey <grog@lemis.com> To: Terry Lambert <tlambert@primenet.com> Cc: John Baldwin <jhb@FreeBSD.ORG>, Daniel Eischen <eischen@vigrid.com>, arch@FreeBSD.ORG, Alfred Perlstein <bright@wintelcom.net>, Mark Murray <mark@grondar.za>, Jake Burkholder <jburkhol@home.com>, Boris Popov <bp@butya.kz>, freebsd-smp@FreeBSD.ORG Subject: Re: Mutexes and semaphores Message-ID: <20001007132752.A28665@wantadilla.lemis.com> In-Reply-To: <200009251938.MAA29311@usr02.primenet.com>; from tlambert@primenet.com on Mon, Sep 25, 2000 at 07:38:22PM %2B0000 References: <20001005113139.C27736@fw.wintelcom.net> <200010052142.OAA15421@usr05.primenet.com> <XFMail.000925100353.jhb@FreeBSD.org> <200009251938.MAA29311@usr02.primenet.com>
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On Monday, 25 September 2000 at 19:38:22 +0000, Terry Lambert wrote: >>> If we are going to support recursive mutex, I think it would be >>> better to add separate calls/macros/data types to support them, >>> so the the mtx mutexes can be simplified. Calls to mtx_enter >>> with the recursive mutex type wouldn't even compile. >> >> Err, the recursive nature of the mutexes is very trivial. It >> doesn't affect the complexity of the mutexes at all. > > Yes, it does. Ownership precludes hand-off. Recusrion support > implies permission and tacit approval. > > A mutex is not recursive. There are things you simply can not > implement when recursion is permitted for all of your primitives. > > The most obvious argument is still that a mutex is intended to > protect data, not code. Recursion is only required if the mutex > is actually protecting reentrancy of code, not access to data. On Thursday, 5 October 2000 at 21:42:28 +0000, Terry Lambert wrote: >>> There is another problem; printf's inside a kthread corrupt like >>> crazy. They look very unthreadsafe. >> >> do NOT use printf without Giant. > > This strikes me as being rather inane. > > If printf won't work without holging the lock, then it damn well > should acquire the lock if it isn't already held, and release it > if it acquired it, before returning. Make up your mind. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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