TestAndSetSemaphore()

uint32_t SRL::System::TestAndSetSemaphore ( uint32_t semaphore )

inlinestatic

Atomically test and set a system semaphore.

Parameters

semaphore

Semaphore number to test and set

Returns

Previous value: 0 if the semaphore was free (now acquired), non-zero if it was already held

Calls the BIOS entry at 0x6000330. Internally uses the SH-2 TAS.B (Test And Set) instruction for atomic read-modify-write.

Warning

Many emulators (including Mednafen) do not correctly emulate the TAS.B instruction's bus cycle. This function may return incorrect results in emulated environments.

Example:

if (System::TestAndSetSemaphore(5) == 0) {
    // Semaphore acquired - critical section
    System::ClearSemaphore(5);
}

See also

ClearSemaphore()