What does this mean?

[John Pugh]

I'm learning VB.NET (I barely have a grip on classes,
inheritance and polymorphism though), and I was looking
at some of the terms on the MSDN site. What does it mean
if something is "thread safe" or not?

Thanks

 

[Ken Tucker [MVP]]

Hi,

Threads are procedures run in the background. Thread safe means it
can safely be run in the background.

Ken
---------------
I'm learning VB.NET (I barely have a grip on classes,
inheritance and polymorphism though), and I was looking
at some of the terms on the MSDN site. What does it mean
if something is "thread safe" or not?

Thanks

 

[rawCoder]

If there are no issues when two threads access some code then its said to be
Thread Safe.
HTH
rawCoder

 

[Ahmed]

Lets say that you have two functions (methods) running simultaneously

Function A and Function B. Or we can call them: Thread A and Thread
B. Both these functions update and read from a variable C. What would
happened if both Thread A and B try to update the variable C at the
same time? if the variable is not thread safe, the data gets corrupted.
if it is thread safe however, it should be done smoothly.


Ahmed

 

[Steve Long]

You could make C threadsafe by using this code:

System.Threading.Interlocked.Increment(C)

if all you wanted to do was increment the variable C.
Otherwise, in VB you can do:

SyncLock Me
'do something with C
End SyncLock

 

[Ahmed]

I was just explaining the difference between thread safe and not thread
safe. but thanks for the info.

 

[Timothy Casey]

There is one other potential problem:

If function A is intermittently updating C, and function B is called in a
context that does not anticipate the activities of function A, then the
value of Function B will deviate from what was intended.

So it is important to remember that being thread-safe is no guarantee
against the usual problems associated with public/global variables and their
equivalents...