Subj : Re: Challenge: Multithreading & Synchronization
To   : comp.programming.threads
From : Giancarlo Niccolai
Date : Sat May 21 2005 03:17 pm

Uenal Mutlu wrote:

> "Giancarlo Niccolai" wrote
>> Maciej Sobczak wrote:
>>
>> > Uenal Mutlu wrote:
>> >
>> >>>The terminal?
>> >>
>> >> Of course:
>> >> Question: Is in your application the terminal shared by multiple
>> >> threads? Answer: YES
>> >> Then: make the terminal lockable
>> >
>> > No. I have specifically used the puts() function to show you that there
>> > are cases where there might be no "object" which you can "physically"
>> > grab and wrap. This example was extremely simple, yet you have rejected
>> > to see the point and have converted the example to use cout - just to
>> > fit it to your broken idea?
>> >
>> > Let's say there is no cout, but instead the "print" function:
>> >
>> > print("I'm doing something");
>>
>> More. The terminal operation may be a LONG operation. If a terminal get
>> disconnected while accessed, it may even be a kind of neverending
>> operation. Cancelation problem apart (which Mutlu seems not to know as he
>> speaks only about windows primitive), that may kill your thread while
>> holding the terminal mutex, it is not correct to lock an OPERATION
>> complex as a terminal output to secure the access to terminal OBJECT.
>> Locking an operation (print) to protect an object (terminal) is wrong.
>>
>> You must find another way to output to the terminal in a way that won't
>> be interfered by other threads. The way exists, and it's simple, just
>> look a little further...
>>
>> The solution applies to all long operations applied to complex object, as
>> database updates.
> 
> I don't know of what database you are talking, but maybe you can enlighten
> us. So, just what is *your* solution to the problem?
> Some pseudo-code will fully suffice. Let's know.

Mine?

To name few:
- firebird/interbase
- oracle
- my-sql
- postgresql

The first two implement a transation registration system. The others a
record level lock granularity, with a reflection on the database structure.
Neither require the complete lock of the database for an update.

Have a good book, please.

Giancarlo.

.