Article View: borland.public.cppbuilder.nativeapi
Article #7551Re: Accessing same variable from multiple threads
From: Alan Bellingham
Date: Wed, 19 Jan 2005 18:38
Date: Wed, 19 Jan 2005 18:38
23 lines
2011 bytes
2011 bytes
"Vladimir Afanasyev" <avv@systema.kiev.ua> wrote: >If both threads works asynchronously - one modifies when want, >another reads when want then no need any critical sections and >semaphors for both threads. If there are _any_ threads that modify the variable, then all threads must cooperate to ensure that it is only modified when none are also trying to read it. Otherwise, the writing thread may have partially updated it when a reading thread attempts to read it. If it's a primitive, and you only have a single processor machine with no ability to actually execute more than one thread at a time, then I don't think you will see thread switching in the middle of the write. However, some of us already have multi-processor PCs, and also hyperthreading and multi-core CPUs will be increasingly common in the near future. With these, I think even a primitive is no longer safe. Alan Bellingham -- ACCU Conference 2005 - 20-23 April, Randolph Hotel, Oxford, UK
Technical Details
Message-ID:
<qu9tu0hgv4gqnlvv65nqq70ua4v73jv0mu@4ax.com>Path:
arc1-ca.pugleaf.net!g2news1.google.com!news4.google.com!news.glorb.com!tiscali!newsfeed1.ip.tiscali.net!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!newsgroups.borland.com!not-for-mailReferences:
<41edea6b@newsgroups.borland.com> <41ee3727$1@newsgroups.borland.com> <41ee742e$1@newsgroups.borland.com> <41ee8f57$1@newsgroups.borland.com>Show Full Headers
Complete Article Headers
X-Google-Thread: 10cc67,4809cdd9a7828fa7 X-Google-Attributes: gid10cc67,public X-Google-Language: ENGLISH,ASCII-7-bit From: Alan Bellingham <alanb@episys.com> Newsgroups: borland.public.cppbuilder.nativeapi Subject: Re: Accessing same variable from multiple threads Date: Wed, 19 Jan 2005 18:38:19 +0000 Reply-To: alanb@episys.com Message-ID: <qu9tu0hgv4gqnlvv65nqq70ua4v73jv0mu@4ax.com> References: <41edea6b@newsgroups.borland.com> <41ee3727$1@newsgroups.borland.com> <41ee742e$1@newsgroups.borland.com> <41ee8f57$1@newsgroups.borland.com> X-Newsreader: Forte Agent 2.0/32.652 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 193.129.251.130 X-Trace: newsgroups.borland.com 1106159898 193.129.251.130 (19 Jan 2005 10:38:18 -0800) Lines: 23 Path: arc1-ca.pugleaf.net!g2news1.google.com!news4.google.com!news.glorb.com!tiscali!newsfeed1.ip.tiscali.net!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!newsgroups.borland.com!not-for-mail