Re: Should I use mutex in this context?
swtbase@gmail.com wrote:
My program has two threads; one main thread and other working thread.
My main thread asks the worker thread to terminate if system is
shutting down by making true a boolean value which is a global shared
resource. The main thread only writes to the global value and the
worker thread only reads the same value. In this context, is mutex use
necessary?
Yes. The problem here is not actually the atomicity but the visibility of
the flag.
Note that there are other ways to do it which sometimes work better: use an
event object or an atomic int.
Event:
main()
ev = CreateEvent(..)
th = CreateThread( &thread, ev, ..)
...
SetEvent(ev)
WaitForSingleObject(th)
CloseHandle(th)
CloseHandle(ev)
thread(ev)
while WaitForSingleObject(ev)==TIMEOUT
...
Atomic integer:
main()
LONG volatile flag;
th = CreateThread( &thread, &flag)
...
InterlockedIncrement(&flag)
WaitForSingleObject(th)
CloseHandle(th)
thread(pflag)
while *pflag==0
...
The advantage of the event is that you can use it with
WaitForMultipleObjects(), which allows you to e.g. move network handling to
a thread and wait for either the shutdown event or any incoming connections
or traffic.
Uli
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