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Thread safety question
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Thread safety question




I have an object that lazily initializes it's variables when accessed and I want it to be thread safe, but I would like to avoid locking and unlocking the lock everytime every method is called.

Below is one solution, but I don't think it is thread safe. I'm assuming that if variable_initialized is YES, then dataPtr must be valid, but I'm afraid that the OS might not guarantee when and how data is flushed, so could it be possible for variable_initialized and myVariable to be invalid?


BOOL variable_initialized=NO;
void* myVariable;
NSLock* myLock; // assume lock has been initialized in main

- (void)isThisThreadSafe;
{
if ( !variable_initialized )
{
[myLock lock];


if ( !variable_initialized )
myVariable = allocateStuff();


variable_initialized = YES;
[myLock unlock];
}


return myVariable;
}

Can anyone confirm this, or offer advice on an alternate solution?

Thanks.

-steve

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