multi thread sync question

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Okay I am working on a multithreaded application. I dont have any code to provide as I havent started it. Im trying to find out how to sync data access. It is going to be a data tree. The tree can be read by multiple threads at the same time. But as soon as a thread need to delete a node all read access need to be locked until the delete is complete. And only one thread can delete a node at a time. From all my research I have found ways to allow one thread access at a time for read or delete through use of mutex. But I havent found a way to allow multiple reads at the same time while locking reads while deleting. If someone could just point me in a good direction. To a good tutorial that would help me greatly. Thanks

Posted 22-Feb-12 13:05pm

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Sergey Alexandrovich Kryukov 22-Feb-12 20:27pm

OS?
--SA

3 solutions

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Espen Harlinn · Answer 1 · 2012-02-22T13:25:00

Solution 1

You could use:
ACE_RW_Thread_Mutex[^] or boost::shared_mutex[^]

Boost homepage[^]
Ace homepage[^]

Best regards
Espen Harlinn

Posted 22-Feb-12 13:25pm

Espen Harlinn

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Sergey Alexandrovich Kryukov 22-Feb-12 20:28pm

Sure, a 5.
--SA

Espen Harlinn 23-Feb-12 5:51am

Thank you Sergey!

Ashish Tyagi 40 23-Feb-12 0:23am

Perfect!!!!!!!!! +5ved

Espen Harlinn 23-Feb-12 5:51am

Thank you Ashish!

Sergey Alexandrovich Kryukov 9-Mar-12 12:47pm

Hi Espen,

Can I ask you to advise on a somewhat related question?
Please take a look at this question:

http://www.codeproject.com/Questions/343545/Starting-a-thread-from-a-thread-within-a-class

Please also take a look on other posts on the page, including my answer.

OP got a very right idea but she messed up things a bit ;-). The question in C++, and I actually answered in full, but my most advanced samples are mine, and only for .NET. Nevertheless, the recipe is given. The idea is to use instance method instead of the static method (required by _beginthreadex) with the work-around: passing "this" additionally. This static method can call the instance method (which becomes a "true" thread method) explicitly, using passed instance pointer. Pretty simple. But my further step is making well-encapsulated thread wrapper which I demonstrated only for .NET.

I would expect that at least one of the C++ libraries you know does exactly this: we could find out a ready-to use C++ base class encapsulating the thread and providing good object-oriented thread interface for derived classes. I would write such thing by myself, but a ready-to-use library would be really nice. Am I right? If you could find such class or template class, could advise on that? If you could find out and post this as another answer, it would be a perfect one.

If you do, please notify me as well; I would be interested to take a look.

How about that?
--SA

Espen Harlinn 10-Mar-12 5:14am

I've added a reply to the question - referring to http://www.codeproject.com/Articles/143484/Integrating-ACE-and-ATL
which more or less implements the design you proposed :-D

Sergey Alexandrovich Kryukov 10-Mar-12 22:56pm

Thank you, I commented and up-voted your answer.
--SA

Espen Harlinn 11-Mar-12 5:07am

I saw, thanks again :-D

Chuck O'Toole · Answer 2 · 2012-02-22T14:39:00

Solution 2

What you have is the classic "Multiple Readers / Single Writer Lock" problem. Lots of people have written articles and solutions to this.

Bing Search[^] will reveal many sources of information and algorithms to implement that.

Posted 22-Feb-12 14:39pm

Chuck O'Toole

Eytukan · Answer 3 · 2012-02-22T20:04:00

From all my research I have found ways to allow one thread access at a time for read or delete through use of mutex. But I havent found a way to allow multiple reads at the same time while locking reads while deleting.

Reading the node would never need sync-ing.
It's only when you try to delete or modify the node. If it's within process you could use critical section to remove nodes from the tree.