std\sys\thread/
windows.rs

1use core::ffi::c_void;
2
3use crate::ffi::CStr;
4use crate::num::NonZero;
5use crate::os::windows::io::{AsRawHandle, HandleOrNull};
6use crate::sys::handle::Handle;
7use crate::sys::pal::time::WaitableTimer;
8use crate::sys::pal::{dur2timeout, to_u16s};
9use crate::sys::{c, stack_overflow};
10use crate::sys_common::FromInner;
11use crate::time::Duration;
12use crate::{io, ptr};
13
14pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
15
16pub struct Thread {
17    handle: Handle,
18}
19
20impl Thread {
21    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
22    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
23    pub unsafe fn new(
24        stack: usize,
25        _name: Option<&str>,
26        p: Box<dyn FnOnce()>,
27    ) -> io::Result<Thread> {
28        let p = Box::into_raw(Box::new(p));
29
30        // CreateThread rounds up values for the stack size to the nearest page size (at least 4kb).
31        // If a value of zero is given then the default stack size is used instead.
32        // SAFETY: `thread_start` has the right ABI for a thread's entry point.
33        // `p` is simply passed through to the new thread without being touched.
34        let ret = unsafe {
35            let ret = c::CreateThread(
36                ptr::null_mut(),
37                stack,
38                Some(thread_start),
39                p as *mut _,
40                c::STACK_SIZE_PARAM_IS_A_RESERVATION,
41                ptr::null_mut(),
42            );
43            HandleOrNull::from_raw_handle(ret)
44        };
45        return if let Ok(handle) = ret.try_into() {
46            Ok(Thread { handle: Handle::from_inner(handle) })
47        } else {
48            // The thread failed to start and as a result p was not consumed. Therefore, it is
49            // safe to reconstruct the box so that it gets deallocated.
50            unsafe { drop(Box::from_raw(p)) };
51            Err(io::Error::last_os_error())
52        };
53
54        unsafe extern "system" fn thread_start(main: *mut c_void) -> u32 {
55            // Next, reserve some stack space for if we otherwise run out of stack.
56            stack_overflow::reserve_stack();
57            // Finally, let's run some code.
58            // SAFETY: We are simply recreating the box that was leaked earlier.
59            // It's the responsibility of the one who call `Thread::new` to ensure this is safe to call here.
60            unsafe { Box::from_raw(main as *mut Box<dyn FnOnce()>)() };
61            0
62        }
63    }
64
65    pub fn join(self) {
66        let rc = unsafe { c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE) };
67        if rc == c::WAIT_FAILED {
68            panic!("failed to join on thread: {}", io::Error::last_os_error());
69        }
70    }
71
72    pub fn handle(&self) -> &Handle {
73        &self.handle
74    }
75
76    pub fn into_handle(self) -> Handle {
77        self.handle
78    }
79}
80
81pub fn available_parallelism() -> io::Result<NonZero<usize>> {
82    let res = unsafe {
83        let mut sysinfo: c::SYSTEM_INFO = crate::mem::zeroed();
84        c::GetSystemInfo(&mut sysinfo);
85        sysinfo.dwNumberOfProcessors as usize
86    };
87    match res {
88        0 => Err(io::Error::UNKNOWN_THREAD_COUNT),
89        cpus => Ok(unsafe { NonZero::new_unchecked(cpus) }),
90    }
91}
92
93pub fn current_os_id() -> Option<u64> {
94    // SAFETY: FFI call with no preconditions.
95    let id: u32 = unsafe { c::GetCurrentThreadId() };
96
97    // A return value of 0 indicates failed lookup.
98    if id == 0 { None } else { Some(id.into()) }
99}
100
101pub fn set_name(name: &CStr) {
102    if let Ok(utf8) = name.to_str() {
103        if let Ok(utf16) = to_u16s(utf8) {
104            unsafe {
105                // SAFETY: the vec returned by `to_u16s` ends with a zero value
106                set_name_wide(&utf16)
107            }
108        };
109    };
110}
111
112/// # Safety
113///
114/// `name` must end with a zero value
115pub unsafe fn set_name_wide(name: &[u16]) {
116    unsafe { c::SetThreadDescription(c::GetCurrentThread(), name.as_ptr()) };
117}
118
119pub fn sleep(dur: Duration) {
120    fn high_precision_sleep(dur: Duration) -> Result<(), ()> {
121        let timer = WaitableTimer::high_resolution()?;
122        timer.set(dur)?;
123        timer.wait()
124    }
125    // Attempt to use high-precision sleep (Windows 10, version 1803+).
126    // On error fallback to the standard `Sleep` function.
127    // Also preserves the zero duration behavior of `Sleep`.
128    if dur.is_zero() || high_precision_sleep(dur).is_err() {
129        unsafe { c::Sleep(dur2timeout(dur)) }
130    }
131}
132
133pub fn yield_now() {
134    // This function will return 0 if there are no other threads to execute,
135    // but this also means that the yield was useless so this isn't really a
136    // case that needs to be worried about.
137    unsafe {
138        c::SwitchToThread();
139    }
140}
std\sys\thread/windows.rs

std\sys\thread/
windows.rs
