windows: provide more accurate result for available_parallelism if cores > 64

Author: klensy

library/std/src/sys/windows/c/windows_sys.lst

@@ -2477,11 +2477,11 @@ Windows.Win32.System.Pipes.PIPE_TYPE_BYTE
 Windows.Win32.System.Pipes.PIPE_TYPE_MESSAGE
 Windows.Win32.System.Pipes.PIPE_WAIT
 Windows.Win32.System.SystemInformation.GetSystemDirectoryW
-Windows.Win32.System.SystemInformation.GetSystemInfo
 Windows.Win32.System.SystemInformation.GetSystemTimeAsFileTime
 Windows.Win32.System.SystemInformation.GetWindowsDirectoryW
 Windows.Win32.System.SystemInformation.PROCESSOR_ARCHITECTURE
 Windows.Win32.System.SystemInformation.SYSTEM_INFO
+Windows.Win32.System.SystemServices.ALL_PROCESSOR_GROUPS
 Windows.Win32.System.SystemServices.DLL_PROCESS_DETACH
 Windows.Win32.System.SystemServices.DLL_THREAD_DETACH
 Windows.Win32.System.SystemServices.EXCEPTION_MAXIMUM_PARAMETERS
@@ -2513,6 +2513,7 @@ Windows.Win32.System.Threading.DEBUG_PROCESS
 Windows.Win32.System.Threading.DETACHED_PROCESS
 Windows.Win32.System.Threading.ExitProcess
 Windows.Win32.System.Threading.EXTENDED_STARTUPINFO_PRESENT
+Windows.Win32.System.Threading.GetActiveProcessorCount
 Windows.Win32.System.Threading.GetCurrentProcess
 Windows.Win32.System.Threading.GetCurrentProcessId
 Windows.Win32.System.Threading.GetCurrentThread

library/std/src/sys/windows/c/windows_sys.rs

@@ -219,6 +219,10 @@ extern "system" {
     pub fn FreeEnvironmentStringsW(penv: PCWSTR) -> BOOL;
 }
 #[link(name = "kernel32")]
+extern "system" {
+    pub fn GetActiveProcessorCount(groupnumber: u16) -> u32;
+}
+#[link(name = "kernel32")]
 extern "system" {
     pub fn GetCommandLineW() -> PCWSTR;
 }
@@ -338,10 +342,6 @@ extern "system" {
     pub fn GetSystemDirectoryW(lpbuffer: PWSTR, usize: u32) -> u32;
 }
 #[link(name = "kernel32")]
-extern "system" {
-    pub fn GetSystemInfo(lpsysteminfo: *mut SYSTEM_INFO) -> ();
-}
-#[link(name = "kernel32")]
 extern "system" {
     pub fn GetSystemTimeAsFileTime(lpsystemtimeasfiletime: *mut FILETIME) -> ();
 }
@@ -822,6 +822,7 @@ impl ::core::clone::Clone for ADDRINFOA {
 pub const AF_INET: ADDRESS_FAMILY = 2u16;
 pub const AF_INET6: ADDRESS_FAMILY = 23u16;
 pub const AF_UNSPEC: ADDRESS_FAMILY = 0u16;
+pub const ALL_PROCESSOR_GROUPS: u32 = 65535u32;
 #[repr(C)]
 pub union ARM64_NT_NEON128 {
     pub Anonymous: ARM64_NT_NEON128_0,

library/std/src/sys/windows/thread.rs

@@ -101,15 +101,13 @@ impl Thread {
 
 pub fn available_parallelism() -> io::Result<NonZeroUsize> {
     let res = unsafe {
-        let mut sysinfo: c::SYSTEM_INFO = crate::mem::zeroed();
-        c::GetSystemInfo(&mut sysinfo);
-        sysinfo.dwNumberOfProcessors as usize
+        // FIXME: windows::Win32::System::SystemServices::ALL_PROCESSOR_GROUPS should be u16, not u32
+        // FIXME: if you need even more accurate result on 32-bit Windows with more, than 64 cores,
+        // consider implementing this using GetLogicalProcessorInformationEx
+        c::GetActiveProcessorCount(c::ALL_PROCESSOR_GROUPS as u16) as usize
     };
     match res {
-        0 => Err(io::const_io_error!(
-            io::ErrorKind::NotFound,
-            "The number of hardware threads is not known for the target platform",
-        )),
+        0 => Err(io::Error::last_os_error()),
         cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus) }),
     }
 }