pthread_mutex_lock in ANSI C vs using Atomic builtins of GCC
I have a program which has 7-8 threads, and lots of shared variables; these variables (and also they may not the primitive type, they may be enum or struct ), then they may read/write by different threads at the same time.
Now, my design is like this,
Is it enough to guarantee that only a thread can write/read shared variables at the same time?
Yes, the pthread solution more than sufficiently protects it. (A pthread_rwlock would let readers operate at the same time and only block them for writes.)
If the gcc atomic operations are truly atomic, getva shouldn't ever return garbage.
Yes, the pthread solution more than sufficiently protects it. (A pthread_rwlock would let readers operate at the same time and only block them for writes.)
If the gcc atomic operations are truly atomic, getva shouldn't ever return garbage.
I have a question, if a shared variable may read/write by some threads and with pthread_mutex_lock(), is the variable requires a 'volatile'?
e.g.
---------- Post updated at 01:03 PM ---------- Previous update was at 01:02 PM ----------
I am sorry, it should be:
Quote:
Originally Posted by fpmurphy
I assume that this is a typo - the second pthread_mutex_lock() should be a pthread_mutex_unlock().
"volatile" has nothing to do with atomic, "volatile" just tells the compiler to never assume that variable is whatever it set it to last. (otherwise, it might assume it never changes and hardcode it in the instructions.)
No variables (except the gcc atomic extensions) are guaranteed to be atomic, at all, ever. There's other problems than being atomic, too -- on a multicore system, one core might have a different copy of the memory still in cache, causing even "volatile" to fail. You need to inform other cores you're modifying values out from under them, which is what memory barriers are for. pthreads does memory barriers for you. I don't know if gcc atomic ops do.
Last edited by Corona688; 08-26-2010 at 05:33 PM..
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Hi
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Executive summary:
Code (posted below) cores in AIX 5.3, despite being compiled and run successfully on several other operating systems. Code is attempting to verify that pthread_mutex_lock can be successfully aborted by siglongjmp. I do not believe this is an unreasonable requirement.
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Hi,
I am creating a file in Unix using a shell script. The file is getting created in the Unix - ANSI format. My requirement is to convert it to the PC - ANSI format. Can anyone tell me how to do this?
Thanks,
Sunil (0 Replies)