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I just wouldn't want to start messing around trying to work out interactions between multiple lock-free updates to [email protected] Saw: Your second comment says that interlocked operations "lock" at some stage; the term "lock" generally implies that one task can maintain exclusive control of a resource for an unbounded length of time; the primary advantage of lock-free programming is that it avoids the danger of resource becoming unusable as a result of the owning task getting waylaid. For example, it can still be cached in things the CPU's L2 cache because they're made coherent in hardware. Volatile is definitely not what you're after - it simply tells the compiler to treat the variable as always changing even if the current code path allows the compiler to optimize a read from memory otherwise. if m_Var is set to false in another thread but it's not declared as volatile, the compiler is free to make it an infinite loop (but doesn't mean it always will) by making it check against a CPU register (e.g.
The bus synchronization used by the interlocked class isn't just "generally faster"--on most systems it has a bounded worst-case time, whereas locks do not. EAX because that was what m_Var was fetched into from the very beginning) instead of issuing another read to the memory location of m_Var (this may be cached - we don't know and don't care and that's the point of cache coherency of x86/x64).
If you have time to spend changing the code then find a way to make it less multithreaded!
Don't find a way to make the multithreaded code more dangerous and easily broken! When incrementing a counter on one thread and reading it on another it seems like you need both a lock (or an Interlocked) and the volatile keyword. This is safe, as it effectively does the read, increment, and write in 'one hit' which can't be interrupted.
is not volatile, thread A may write five times, but thread B may see those writes as being delayed (or even potentially in the wrong order).
Another thread could change the value after you've read but before you write back.Unless you require no cache coherency, such as a graphics card, PCI device etc, you wouldn't set a cache line to write-through.Yes, everything you say is if not 100% at least 99% on the mark.However, it doesn't mean that not declaring volatile will cause the loop to go on infinitely - specifying volatile only guarantees that it won't if m_Var is set to false in another [email protected] Saw: Under the memory model for C , volatile is how you've described it (basically useful for device-mapped memory and not a lot else).Under the memory model for the CLR (this question is tagged C#) is that volatile will insert memory barriers around reads and writes to that storage location.