Frank Church wrote 6 lines
I am writing an app involving 2 threads, and a timer loop in the UI.
The first thread monitors network events, logs them into a database, appends
them to a list.
Any time I see append to a list I always think "RTLCriticalSection"
Show quoted text 8 lines
The second thread monitors the list, checks the events and updates a data
structure, which is used by a timer loop in the main application to update
the UI.
What are the issues involved in making sure that the 2 threads don't
conflicted over access to the list?
This is my first foray into using threads that share memory structures.
You have to protect the list from access by other threads. CritcialSection is the only way
InitCriticalSection - Creates it
DoneCriticalSection - Frees it
EnterCriticalSection - Locks list
DoneCritiicalSection - Unlocks list
Example
EnterCriticalSection(FLock);
Try
FList.Add(EntryP);
Finally
LeaveCriticalSection(FLock);
end;
Polling where the list size is highly dynamic you will need protect it. I think FPC has thread safe list objects too.
See the FPC rtl.pdf documentation on TThreadList
2.63.1
TThreadList
Description
TThreadList is a thread-safe Tlist (307) implementation. Unlike TList, it can be accessed read-
write by multiple threads: the list implementation will take care of locking the list when adding or
removing items from the list.
