Suspend/Resume all user processes - Is that possible? - c

Question

I have PC's with a lot of applications running at once, i was thinking is it possible to SUSPEND all applications, i want to do that to run periodically one other application that is using a lot the CPU so want it to have all the processor time.
The thing is i want to suspend all applications run my thing that uses the CPU a lot, then when my thingy exit, to resume all applications and all work to be resumed fine....
Any comments are welcome.

Answer 1

It's possible but not recommended at all.
Set the process and thread priority so your application will be given a larger slice of the CPU.
This also means it won't kill the desktop, any network connections, antivirus, start menu, the window manager, etc as your method will.

Answer 2

You could possibly keep a list that you yourself manually generate of programs that are too demanding (say, for (bad) example, Steam.exe, chrome.exe, 90GB-video-game.exe, etc). Basically, you get the entire list of all running processes, search that list for all of the blacklisted names, and NtSuspendProcess/NtResumeProcess (should you need to allow it to run again in the future).
I don't believe suspending all user processes is a good idea. Much of those are weirdly protected and probably should remain running, anyway, and it's an uphill battle with very little to gain.
As mentioned in another answer, you can of course just adjust your processes priority up if you have permission to do so. This sorts the OS-wide process list in favor of your process, so you get CPU time first.
Here's an example of something similar to your original request. I'm writing a program in C++ that needed this exact feature, so I figured I'd help out. This will find Steam.exe or chrome.exe, and suspend the first one it finds for 10 seconds.. then will resume it. This will show as "not responding" on Windows if you try to interact with the window whilst it's suspended. Some applications may not like being suspended, YMMV.
/*Find, suspend, resume Win32 C++
*Written by jimmio92. No rights reserved. Public domain.
*NO WARRANTY! NO LIABILITY! (obviously)
*/
#include <windows.h>
#include <psapi.h>
typedef LONG (NTAPI *NtSuspendProcess)(IN HANDLE ProcessHandle);
typedef LONG (NTAPI *NtResumeProcess)(IN HANDLE ProcessHandle);
NtSuspendProcess dSuspendProcess = nullptr;
NtResumeProcess dResumeProcess = nullptr;
int get_the_pid() {
DWORD procs[4096], bytes;
int out = -1;
if(!EnumProcesses(procs, sizeof(procs), &bytes)) {
return -1;
}
for(size_t i = 0; i < bytes/sizeof(DWORD); ++i) {
TCHAR name[MAX_PATH] = "";
HMODULE mod;
HANDLE p = nullptr;
bool found = false;
p = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, procs[i]);
if(p == nullptr)
continue;
DWORD unused_bytes_for_all_modules = 0;
if(EnumProcessModules(p, &mod, sizeof(mod), &unused_bytes_for_all_modules)) {
GetModuleBaseName(p, mod, name, sizeof(name));
//change this to use an array of names or whatever fits your need better
if(strcmp(name, "Steam.exe") == 0 || strcmp(name, "chrome.exe") == 0) {
out = procs[i];
found = true;
}
}
CloseHandle(p);
if(found) break;
}
return out;
}
void suspend_process_by_id(int pid) {
HANDLE h = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
if(h == nullptr)
return;
dSuspendProcess(h);
CloseHandle(h);
}
void resume_process_by_id(int pid) {
HANDLE h = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
if(h == nullptr)
return;
dResumeProcess(h);
CloseHandle(h);
}
void init() {
//load NtSuspendProcess from ntdll.dll
HMODULE ntmod = GetModuleHandle("ntdll");
dSuspendProcess = (NtSuspendProcess)GetProcAddress(ntmod, "NtSuspendProcess");
dResumeProcess = (NtResumeProcess)GetProcAddress(ntmod, "NtResumeProcess");
}
int main() {
init();
int pid = get_the_pid();
if(pid < 0) {
printf("Steam.exe and chrome.exe not found");
}
suspend_process_by_id(pid);
//wait ten seconds for demonstration purposes
Sleep(10000);
resume_process_by_id(pid);
return 0;
}