Date: Thu, 10 Dec 1998 14:20:22 -0800 (PST) From: Marc Slemko <marcs@znep.com> To: "Richard Seaman, Jr." <lists@tar.com> Cc: "hackers@freebsd.org" <hackers@FreeBSD.ORG> Subject: Re: pread/pwrite Message-ID: <Pine.BSF.4.05.9812101418070.463-100000@alive.znep.com> In-Reply-To: <199812102156.PAA27450@ns.tar.com>
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On Thu, 10 Dec 1998, Richard Seaman, Jr. wrote: > I don't know if there is any interest in X/Open pread, pwrite > calls. Essentially, they implement atomic seek/write and > atomic seek/read calls. They are more useful in threaded > apps where you would need a file lock between a seek/write > or seek/read, but even in single threaded apps can allow > you to avoid a syscall. > > Attached is an implementation. If there is interest, and > if the implementation meets with approval, I'll submit > a PR. Or, perhaps someone would want to commit it directly. > > I welcome any comments. (not necessarily addressed specifically at pread/pwrite, but it does apply to it because of how it is used...) Where is the locking if multiple threads are reading and/or writing from or to the same descriptor at the same time? If you have x threads reading from a descriptor opened from a file on disk, do x-1 of them have to wait until the first one finishes before they can do anything? What about with mixed reading/writing? To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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