CODEWITHSUNDEEP
c++futex
Ebony Ayers
Ebony Ayers

Reputation: 360

How compare to a constant with WaitOnAddress

In Linux, futexs have the following signature long futex(uint32_t *uaddr, int futex_op, uint32_t val, const struct timespec *timeout), so I can say syscall(SYS_futex, &m_address, FUTEX_WAIT_PRIVATE, 1, nullptr); which will pause the current thread if the value at m_address is 1.

What I want to know is how do I do this in windows.

The signature for BOOL WaitOnAddress(volatile VOID *Address, PVOID CompareAddress, SIZE_T AddressSize, DWORD dwMilliseconds). There's no option for a value. Do I have to make a variable with constant value and pass it to CompareAddress or am I missing something?

Upvotes: 0

Views: 170

Answers (1)

Chris Kushnir
Chris Kushnir

Reputation: 247

WaitOnAddress is not used as a single call wait instruction, it is generally called in a loop e.g. Raymond Chen - A helper template function to wait for WaitOnAddress in a loop. Nor will it wake without extra help, whatever code changes the bytes at Address must also call WakeByAddressSingle or WakeByAddressAll to allow any active WaitOnAddress calls to return.

Upvotes: 2

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