I have come across a Lenovo IdeaCentre A540-24ICB system with a scheduled task that wakes the computer to start my application and it seems to start but the system goes back to sleep right away. Sometimes it appears to not start (or goes to sleep so fast nothing is logged yet) so I checked the Windows power sleep options to ensure "Allow wake timers" was enabled but it didn't exist! Searching online I found a registry entry to add to have it show up in the power options and then ensured it's was enabled. However, didn't make a difference.
I have to use the mouse/keyboard for the computer to wake long enough to run the application (it will start where it left off). The application has been used for years and waking and running has worked. It already tells the system to not go to sleep through the api call in the main processing thread (which could take a fraction of a second to get to):
SetThreadExecutionState(ES_CONTINUOUS | ES_SYSTEM_REQUIRED);
I thought that API was enough to prevent system from going to sleep? As mentioned, it has worked for years. It's just this new Lenovo system or the Win10 installed with it doesn't seem to honor it? Is there some other API call that needs to be called? or any checks / fix the app should do to ensure the SetThreadExecutionState() will work?
TIA!!
I'm writing a utility that addresses a Bluetooth status indicator light when my webcam is in use so that I'm not disturbed during meetings while working from home. Presently, I'm parsing the output of lsof to see which processes have a file descriptor open to VDC, but this approach is fraught for a number of reasons:
Not all processes with a FD to VDC are actually using the webcam (ex: avconfere, the Facetime daemon, and Chrome, which always holds a FD if it is open).
Most processes spin up a second process when the webcam is actually in use, and that child process doesn't always share a name in common with its parent, meaning I have to maintain a mapping to know which program is using the webcam.
Some applications (like Zoom) don't release the webcam FD when the webcam stops being used (only when Zoom is killed completely).
Is there any other/better interface for accurately determining which processes are using the webcam? Applications like Oversight lead me to believe that there should be a better method of doing this.
Summary
When putting the monitor in sleep mode in Windows 10, Windows seems to execute some tasks that don't get executed with the screen on.
This is interfering with our software, and we need to get rid of it.
Ful story
For a hardware device with a touch screen, I need to be able to turn off the touch screen when it's not in use, for durability reasons. Windows has a message that you can send to turn it off, SC_MONITORPOWER. More specifically:
SendMessage(hwnd, WM_SYSCOMMAND, SC_MONITORPOWER, 2);
This works fine, but when the screen is off, Windows is apparently sometimes performing some tasks that it doesn't do when the screen is on. We are careful to never write anything to the screen in this situation (that causes huge problems when the screen is off, in fact just having a blinking cursor in a DOS box is using up half a core when the screen is off).
Our software requires a callback to be executed every 0.25 ms. We have turned nearly every task, service and several other things in Windows off, and with the screen on, I can run our software for days without ever missing a callback. But with the screen off I get hiccups. The callback already runs at the highest possible priority.
So there is apparently something that we missed when we turned all services and tasks off. There appear to be 2 causes of hiccups:
One happens once every 10-30 hours or so (not sure of the exact time, it seems to vary). But it always happens 5 times, with EXACTLY 5 minutes (at most a few milliseconds off) in between (so in total it happens 5 times in a 25 minute period).
Beside this, we get a single hiccup typically every 4-10 hours, but the time between occurrences doesn't seem to be very constant so there could also be multiple causes.
I'm a bit at a loss here, and running analysis software can easily interfere with our own software, making it harder to detect when these hiccups really occur and when they are caused by running the analysis software.
Interestingly, I have seen this 5-times-every-5-minutes thing also on a completely different system (different hardware, different OS version), when recording audio in Adobe Audition. Audition misses pieces of audio every 5 minutes in this case, and I think it also only happens when the monitor is in sleep mode and you're not logged in remotely.
We have already tried to turn the touch screen off using direct monitor commands like Nircmd does, and it doesn't support those. My guess is that the SC_MONITORPOWER message is triggering more things in Windows, and if we can turn them off, that would fix our problem. Any ideas?
System
Intel i5-8700 with 6 cores, Windows LTSB, no extra software installed except our own.
Never mind, problem solved. It was not an extra task that was being started, it was one of the existing Windows processes that for some reason only causes issues when the display is off. Since killing them is not an option (Windows will just restart them), I've suspended the following processes, and the culprit is one of these (I don't know which one yet):
sihost.exe
igfxEM.exe (I very much suspect this one)
RuntimeBroker.exe
dllhost.exe
taskhostw.exe
explorer.exe
I have to continue testing a bit longer to be absolutely certain, but so far with these tasks all suspended I've not seen a missed callback in the last 38 hours. I don't know yet if there are any drawbacks to suspending all these things, so I'll try to find the cause(s) and suspend only that/those.
When I try to use alarms to launch voice from my application when it doesn't run in determined times I face a problem.
The audio still running more than one time as I only want it to run once. But it continuo running until the user stop it which is not suitable for my application behavior.
So, is there a way to make alarm audio file run only once in this time?
If no, is there any other way to do that instead of alarms?
Alarm are programmed to be repeated forever. You can't unless you change something in the audio file.
I'm writing a process-controller kernel extension for leopard. The application enables me to suspend process's with SIGSUS and to make the computer sleep. My problem is when an application that uses video / audio (e.g iTunes or GarageBand) is suspended and then I try to make the computer sleep, the sleep process waits on the audio / video application to end with a timeout of 30 seconds. In reality, when I try to put the computer to sleep when an audio / video application is suspended, the computer hangs for 30 seconds (probably the suspended application is not responding to the sleep request) and then it sleeps normally. When I wake the computer and send SIGCON to the video / audio application, it continues normally.
Is there a way to change that 30 second wait time out? Or to make it not wait at all? Or any other solution?
To answer your question it would be helpful to get some more information about what you're trying to do. First, why are you writing a kernel extension? Nothing you've talked about in the problem suggests you need to do this. Second, why are you suspending all of the processes before putting the system to sleep? You should be able to gracefully sleep the system without suspending any processes.