On 8/10/20 14:32, Paul Gofman wrote:
On 8/10/20 13:55, Arkadiusz Hiler wrote:
Sleep() and GetTickCount() work on Windows in 15.6ms increments.
Some programs (DOSBox) are depending on this behavior and are assuming that the return value of GetTickCount() will change during sleeping.
Currently we are updating shared counters used by GetTickCount() every 16ms + on each server request, and our Sleep() implementation has resolution of 1ms, which causes DOSBox to hang.
This patch changes Sleep() (and SleepEx()) to behave the same way as on Windows and makes sure that GetTickCount() will be updated during sleeping by decreasing the update interval to 15ms (worst case, without any server calls).
This fixes Doom II from Steam.
I also did notice that Sleep on Windows use to work with 15.6ms quantum some time ago. But the important part which is missed here is that Sleep behaviour is affected (at least) by timeBeginPeriod() / timeEndPeriod() winmm functions (as I recalled now after rerunning my old test program and wondering why I see 1ms sleep quantum). E. g., if I call timeBeingPeriod(1) before testing Sleep actual time and GetTickCount change, the Sleep starts to behave very similar to how it works now in Wine: sleeps with 1ms quantum and GetTickCount() is not necessarily updated on wake. I think we can't ignore that behaviour, I did see the games playing with winmm functions, Sleep etc.
I was also initially going to say that maybe we would need to explicitly check if GetTickCount has changed during sleep, but the failing test on Win10 suggests that maybe Windows doesn't guarantee that also, just sleeps with 15.6ms quantum by default (unless changed by winmm).
PS If timeBeginPeriod() indeed sets the global time resolution for all processes as the docs suggest, I can guess there should be a field in KSHARED_USER_DATA which holds that resolution (there are a few related to timers, I did not ever test what exactly do they hold), and we should probably use those to store and retrieve timer resolution.