You are right. How about one thread writes, but the other thread only reads?
From: David Chapman [mailto:[email protected]]
Sent: Friday, March 22, 2013 3:46 PM
To: Will Deng
Cc: [email protected]
Subject: Re: [Valgrind-users] Helgrind doesn't handle bit field correctly
On 3/22/2013 3:35 PM, Will Deng wrote:
Even if two threads are writing to the same word, as long as thread 1 doesn't
modify thread_2_data, it should be ok, right?
Nope: the usual way for a processor to do this is to read the entire word,
modify the appropriate bits, and then write the entire word. This is very
definitely a race in your situation. Thread 1 would write the old value of
thread_2_data with the new value of thread_1_data, or vice versa.
--
David Chapman [email protected]<mailto:[email protected]>
Chapman Consulting -- San Jose, CA
Software Development Done Right.
www.chapman-consulting-sj.com<http://www.chapman-consulting-sj.com>
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