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43 lines
2.1 KiB
Plaintext
Path: uutiset.elisa.fi!feeder2.news.elisa.fi!feeder.erje.net!newsfeed.kamp.net!newsfeed0.kamp.net!nx02.iad01.newshosting.com!newshosting.com!post01.iad!not-for-mail
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Sender: jimbo@lews (Jimbo Foobarcuux)
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From: jimbo@slp53.sl.home (Jimbo Foobarcuux)
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Reply-To: slp53@pacbell.net
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Subject: Re: Are writes "atomic" to readers of the file?
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Newsgroups: comp.unix.programmer
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References: <e9065dac-13c1-4103-9e31-6974ca232a89@t15g2000prt.googlegroups.com> <87hbblwelr.fsf@sapphire.mobileactivedefense.com> <pql248-4va.ln1@wilbur.25thandClement.com> <ikns6r$li3$1@Iltempo.Update.UU.SE> <8762s0jreh.fsf@sapphire.mobileactivedefense.com> <ikqqp1$jv0$1@Iltempo.Update.UU.SE> <87hbbjc5jt.fsf@sapphire.mobileactivedefense.com> <ikr0na$lru$1@Iltempo.Update.UU.SE> <tO8cp.1228$GE6.370@news.usenetserver.com> <ikr6ks$nlf$1@Iltempo.Update.UU.SE> <8ioh48-8mu.ln1@leafnode-msgid.gclare.org.uk>
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Organization: UseNetServer - www.usenetserver.com
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X-Complaints-To: abuse@usenetserver.com
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Message-ID: <oktdp.42997$Te.22361@news.usenetserver.com>
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Date: 08 Mar 2011 17:04:20 GMT
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Lines: 27
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Xref: uutiset.elisa.fi comp.unix.programmer:181736
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John Denver <jd@clare.See-My-Signature.invalid> writes:
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>Eric the Red wrote:
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>
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>>> There _IS_ a requirement that all reads and writes to regular files
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>>> be atomic. There is also an ordering guarantee. Any implementation
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>>> that doesn't provide both atomicity and ordering guarantees is broken.
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>>
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>> But where is it specified?
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>
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>The place where it is stated most explicitly is in XSH7 2.9.7
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>Thread Interactions with Regular File Operations:
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>
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> All of the following functions shall be atomic with respect to each
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> other in the effects specified in POSIX.1-2008 when they operate on
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> regular files or symbolic links:
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>
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> [List of functions that includes read() and write()]
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>
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> If two threads each call one of these functions, each call shall
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> either see all of the specified effects of the other call, or none
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> of them.
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>
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And, for the purposes of this paragraph, the two threads need not be
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part of the same process.
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jimbo
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