[thread][eclipse] how to check

[Thomas Richter]

Hi group,
is there a smart way to check whether an application is thread
save? My object are not accessed from different points and all
static methods are syncronized. I used \W[A-Z]\w+\s?\.\w+\(
to find all calls to static function, but I think I have to check
also other method calls ....

wkr Thomas

 

[Thomas Weidenfeller]

is there a smart way to check whether an application is thread
save? My object are not accessed from different points and all
static methods are syncronized. I used \W[A-Z]\w+\s?\.\w+\(
to find all calls to static function, but I think I have to check
also other method calls ....

You work with a fare to simple idea of how threads work. Just
synchronizing all methods (static or not) does not give you a thread
save application.

You need to understand your code and the potential flow of control
through it to identify critical sections of code. No tool in the world
can do this. This is one of the reasons why threads are not for laymen.
You really have to know what you are doing.

Go back to square one. Get a good book about Java threading and start
reading it.

/Thomas

 

[TechBookReport]

is there a smart way to check whether an application is thread
save? My object are not accessed from different points and all
static methods are syncronized. I used \W[A-Z]\w+\s?\.\w+\(
to find all calls to static function, but I think I have to check
also other method calls ....

You work with a fare to simple idea of how threads work. Just
synchronizing all methods (static or not) does not give you a thread
save application.

You need to understand your code and the potential flow of control
through it to identify critical sections of code. No tool in the world
can do this. This is one of the reasons why threads are not for laymen.
You really have to know what you are doing.

Go back to square one. Get a good book about Java threading and start
reading it.

/Thomas

Java Concurrency In Practice, by Brian Goetz, should be that book. It's
excellent - see the review here: http://www.techbookreport.com/tbr0261.html

 

[opalpa opalpa]

http://javapathfinder.sourceforge.net/ attempts to discover concurancy
problems. Pathfinder was created at NASA for things like Java on
rover.

is there a smart way to check whether an application is thread
save?

Using tools helps.

Avoiding settors in classes makes it easier to proove they are safe.

My object are not accessed from different points and all
static methods are syncronized.

Non-static methods too.

Will your code potentially ever be accessed by multiple threads? It
takes alot of thinking to check a lot of classes and be confident the
code behaves correctly in such circumstances.

Are there fields that are non-private? Taking a monitor by
synchronizing a method does not give a monitor for instance variables.

All Swing creation and modification is to happen on Swing thread.

I used \W[A-Z]\w+\s?\.\w+\(
to find all calls to static function, but I think I have to check
also other method calls ....

Why just static methods?

opalpa
(e-mail address removed)
http://opalpa.info/

 

[Thomas Richter]

http://javapathfinder.sourceforge.net/ attempts to discover concurancy
Using tools helps.

Of which tools do you think?

Non-static methods too.

Even if my threads will not access the same objects?

wkr Thomas

 

[opalpa opalpa]

Of which tools do you think?

Other than pathfinder, FindBugs find some concurancy problems.

Even if my threads will not access the same objects?

What about in the future? Not necessarily even on your current
project.

opalpa
(e-mail address removed)
http://opalpa.info/

 

[Thomas Weidenfeller]

Using tools helps.

Only so much. Show me the tool that gives the right answer in the
following rather simple case:

public class SomeClass {
private int someValue;
private int anotherValue;

public synchronized void setSomeValue(int v) {
someValue = v;
}

public synchronized void setAnotherValue(int v) {
anotherValue = v;
}

public void setValues(int a, int b) {
setSomeValue(a);
setAnotherValue(b);
}

...
...
...
}

Question: Is it ok if multiple threads use setValues() concurrently?

(a) If your tool says no, I will argue it might be safe.

(b) If your tool says yes, I will argue it might be unsafe.

(c) If your tool says "I don't know, it depends. You need to check". I
will say thank you very much, I knew that before.

/Thomas

 

[opalpa opalpa]

(c) If your tool says "I don't know, it depends. You need to check". I
will say thank you very much, I knew that before.

Most projects have more than one class. When a tool can go through an
entire source base or entire jar worth of classes and present select
sections for review it helps me.

opalpa
(e-mail address removed)
http://opalpa.info/