std/sys/pal/unix/
thread.rs

1use crate::ffi::CStr;
2use crate::mem::{self, ManuallyDrop};
3use crate::num::NonZero;
4#[cfg(all(target_os = "linux", target_env = "gnu"))]
5use crate::sys::weak::dlsym;
6#[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto",))]
7use crate::sys::weak::weak;
8use crate::sys::{os, stack_overflow};
9use crate::time::{Duration, Instant};
10use crate::{cmp, io, ptr};
11#[cfg(not(any(
12    target_os = "l4re",
13    target_os = "vxworks",
14    target_os = "espidf",
15    target_os = "nuttx"
16)))]
17pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
18#[cfg(target_os = "l4re")]
19pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
20#[cfg(target_os = "vxworks")]
21pub const DEFAULT_MIN_STACK_SIZE: usize = 256 * 1024;
22#[cfg(any(target_os = "espidf", target_os = "nuttx"))]
23pub const DEFAULT_MIN_STACK_SIZE: usize = 0; // 0 indicates that the stack size configured in the ESP-IDF/NuttX menuconfig system should be used
24
25struct ThreadData {
26    name: Option<Box<str>>,
27    f: Box<dyn FnOnce()>,
28}
29
30pub struct Thread {
31    id: libc::pthread_t,
32}
33
34// Some platforms may have pthread_t as a pointer in which case we still want
35// a thread to be Send/Sync
36unsafe impl Send for Thread {}
37unsafe impl Sync for Thread {}
38
39impl Thread {
40    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
41    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
42    pub unsafe fn new(
43        stack: usize,
44        name: Option<&str>,
45        f: Box<dyn FnOnce()>,
46    ) -> io::Result<Thread> {
47        let data = Box::into_raw(Box::new(ThreadData { name: name.map(Box::from), f }));
48        let mut native: libc::pthread_t = mem::zeroed();
49        let mut attr: mem::MaybeUninit<libc::pthread_attr_t> = mem::MaybeUninit::uninit();
50        assert_eq!(libc::pthread_attr_init(attr.as_mut_ptr()), 0);
51
52        #[cfg(any(target_os = "espidf", target_os = "nuttx"))]
53        if stack > 0 {
54            // Only set the stack if a non-zero value is passed
55            // 0 is used as an indication that the default stack size configured in the ESP-IDF/NuttX menuconfig system should be used
56            assert_eq!(
57                libc::pthread_attr_setstacksize(
58                    attr.as_mut_ptr(),
59                    cmp::max(stack, min_stack_size(attr.as_ptr()))
60                ),
61                0
62            );
63        }
64
65        #[cfg(not(any(target_os = "espidf", target_os = "nuttx")))]
66        {
67            let stack_size = cmp::max(stack, min_stack_size(attr.as_ptr()));
68
69            match libc::pthread_attr_setstacksize(attr.as_mut_ptr(), stack_size) {
70                0 => {}
71                n => {
72                    assert_eq!(n, libc::EINVAL);
73                    // EINVAL means |stack_size| is either too small or not a
74                    // multiple of the system page size. Because it's definitely
75                    // >= PTHREAD_STACK_MIN, it must be an alignment issue.
76                    // Round up to the nearest page and try again.
77                    let page_size = os::page_size();
78                    let stack_size =
79                        (stack_size + page_size - 1) & (-(page_size as isize - 1) as usize - 1);
80                    assert_eq!(libc::pthread_attr_setstacksize(attr.as_mut_ptr(), stack_size), 0);
81                }
82            };
83        }
84
85        let ret = libc::pthread_create(&mut native, attr.as_ptr(), thread_start, data as *mut _);
86        // Note: if the thread creation fails and this assert fails, then p will
87        // be leaked. However, an alternative design could cause double-free
88        // which is clearly worse.
89        assert_eq!(libc::pthread_attr_destroy(attr.as_mut_ptr()), 0);
90
91        return if ret != 0 {
92            // The thread failed to start and as a result p was not consumed. Therefore, it is
93            // safe to reconstruct the box so that it gets deallocated.
94            drop(Box::from_raw(data));
95            Err(io::Error::from_raw_os_error(ret))
96        } else {
97            Ok(Thread { id: native })
98        };
99
100        extern "C" fn thread_start(data: *mut libc::c_void) -> *mut libc::c_void {
101            unsafe {
102                let data = Box::from_raw(data as *mut ThreadData);
103                // Next, set up our stack overflow handler which may get triggered if we run
104                // out of stack.
105                let _handler = stack_overflow::Handler::new(data.name);
106                // Finally, let's run some code.
107                (data.f)();
108            }
109            ptr::null_mut()
110        }
111    }
112
113    pub fn yield_now() {
114        let ret = unsafe { libc::sched_yield() };
115        debug_assert_eq!(ret, 0);
116    }
117
118    #[cfg(target_os = "android")]
119    pub fn set_name(name: &CStr) {
120        const PR_SET_NAME: libc::c_int = 15;
121        unsafe {
122            let res = libc::prctl(
123                PR_SET_NAME,
124                name.as_ptr(),
125                0 as libc::c_ulong,
126                0 as libc::c_ulong,
127                0 as libc::c_ulong,
128            );
129            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
130            debug_assert_eq!(res, 0);
131        }
132    }
133
134    #[cfg(any(
135        target_os = "linux",
136        target_os = "freebsd",
137        target_os = "dragonfly",
138        target_os = "nuttx",
139        target_os = "cygwin"
140    ))]
141    pub fn set_name(name: &CStr) {
142        unsafe {
143            cfg_if::cfg_if! {
144                if #[cfg(any(target_os = "linux", target_os = "cygwin"))] {
145                    // Linux and Cygwin limits the allowed length of the name.
146                    const TASK_COMM_LEN: usize = 16;
147                    let name = truncate_cstr::<{ TASK_COMM_LEN }>(name);
148                } else {
149                    // FreeBSD, DragonFly BSD and NuttX do not enforce length limits.
150                }
151            };
152            // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20 for Linux,
153            // FreeBSD 12.2 and 13.0, and DragonFly BSD 6.0.
154            let res = libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
155            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
156            debug_assert_eq!(res, 0);
157        }
158    }
159
160    #[cfg(target_os = "openbsd")]
161    pub fn set_name(name: &CStr) {
162        unsafe {
163            libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
164        }
165    }
166
167    #[cfg(target_vendor = "apple")]
168    pub fn set_name(name: &CStr) {
169        unsafe {
170            let name = truncate_cstr::<{ libc::MAXTHREADNAMESIZE }>(name);
171            let res = libc::pthread_setname_np(name.as_ptr());
172            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
173            debug_assert_eq!(res, 0);
174        }
175    }
176
177    #[cfg(target_os = "netbsd")]
178    pub fn set_name(name: &CStr) {
179        unsafe {
180            let res = libc::pthread_setname_np(
181                libc::pthread_self(),
182                c"%s".as_ptr(),
183                name.as_ptr() as *mut libc::c_void,
184            );
185            debug_assert_eq!(res, 0);
186        }
187    }
188
189    #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
190    pub fn set_name(name: &CStr) {
191        weak!(
192            fn pthread_setname_np(
193                thread: libc::pthread_t,
194                name: *const libc::c_char,
195            ) -> libc::c_int;
196        );
197
198        if let Some(f) = pthread_setname_np.get() {
199            #[cfg(target_os = "nto")]
200            const THREAD_NAME_MAX: usize = libc::_NTO_THREAD_NAME_MAX as usize;
201            #[cfg(any(target_os = "solaris", target_os = "illumos"))]
202            const THREAD_NAME_MAX: usize = 32;
203
204            let name = truncate_cstr::<{ THREAD_NAME_MAX }>(name);
205            let res = unsafe { f(libc::pthread_self(), name.as_ptr()) };
206            debug_assert_eq!(res, 0);
207        }
208    }
209
210    #[cfg(target_os = "fuchsia")]
211    pub fn set_name(name: &CStr) {
212        use super::fuchsia::*;
213        unsafe {
214            zx_object_set_property(
215                zx_thread_self(),
216                ZX_PROP_NAME,
217                name.as_ptr() as *const libc::c_void,
218                name.to_bytes().len(),
219            );
220        }
221    }
222
223    #[cfg(target_os = "haiku")]
224    pub fn set_name(name: &CStr) {
225        unsafe {
226            let thread_self = libc::find_thread(ptr::null_mut());
227            let res = libc::rename_thread(thread_self, name.as_ptr());
228            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
229            debug_assert_eq!(res, libc::B_OK);
230        }
231    }
232
233    #[cfg(target_os = "vxworks")]
234    pub fn set_name(name: &CStr) {
235        let mut name = truncate_cstr::<{ (libc::VX_TASK_RENAME_LENGTH - 1) as usize }>(name);
236        let res = unsafe { libc::taskNameSet(libc::taskIdSelf(), name.as_mut_ptr()) };
237        debug_assert_eq!(res, libc::OK);
238    }
239
240    #[cfg(any(
241        target_env = "newlib",
242        target_os = "l4re",
243        target_os = "emscripten",
244        target_os = "redox",
245        target_os = "hurd",
246        target_os = "aix",
247    ))]
248    pub fn set_name(_name: &CStr) {
249        // Newlib and Emscripten have no way to set a thread name.
250    }
251
252    #[cfg(not(target_os = "espidf"))]
253    pub fn sleep(dur: Duration) {
254        let mut secs = dur.as_secs();
255        let mut nsecs = dur.subsec_nanos() as _;
256
257        // If we're awoken with a signal then the return value will be -1 and
258        // nanosleep will fill in `ts` with the remaining time.
259        unsafe {
260            while secs > 0 || nsecs > 0 {
261                let mut ts = libc::timespec {
262                    tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
263                    tv_nsec: nsecs,
264                };
265                secs -= ts.tv_sec as u64;
266                let ts_ptr = &raw mut ts;
267                if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
268                    assert_eq!(os::errno(), libc::EINTR);
269                    secs += ts.tv_sec as u64;
270                    nsecs = ts.tv_nsec;
271                } else {
272                    nsecs = 0;
273                }
274            }
275        }
276    }
277
278    #[cfg(target_os = "espidf")]
279    pub fn sleep(dur: Duration) {
280        // ESP-IDF does not have `nanosleep`, so we use `usleep` instead.
281        // As per the documentation of `usleep`, it is expected to support
282        // sleep times as big as at least up to 1 second.
283        //
284        // ESP-IDF does support almost up to `u32::MAX`, but due to a potential integer overflow in its
285        // `usleep` implementation
286        // (https://github.com/espressif/esp-idf/blob/d7ca8b94c852052e3bc33292287ef4dd62c9eeb1/components/newlib/time.c#L210),
287        // we limit the sleep time to the maximum one that would not cause the underlying `usleep` implementation to overflow
288        // (`portTICK_PERIOD_MS` can be anything between 1 to 1000, and is 10 by default).
289        const MAX_MICROS: u32 = u32::MAX - 1_000_000 - 1;
290
291        // Add any nanoseconds smaller than a microsecond as an extra microsecond
292        // so as to comply with the `std::thread::sleep` contract which mandates
293        // implementations to sleep for _at least_ the provided `dur`.
294        // We can't overflow `micros` as it is a `u128`, while `Duration` is a pair of
295        // (`u64` secs, `u32` nanos), where the nanos are strictly smaller than 1 second
296        // (i.e. < 1_000_000_000)
297        let mut micros = dur.as_micros() + if dur.subsec_nanos() % 1_000 > 0 { 1 } else { 0 };
298
299        while micros > 0 {
300            let st = if micros > MAX_MICROS as u128 { MAX_MICROS } else { micros as u32 };
301            unsafe {
302                libc::usleep(st);
303            }
304
305            micros -= st as u128;
306        }
307    }
308
309    // Any unix that has clock_nanosleep
310    // If this list changes update the MIRI chock_nanosleep shim
311    #[cfg(any(
312        target_os = "freebsd",
313        target_os = "netbsd",
314        target_os = "linux",
315        target_os = "android",
316        target_os = "solaris",
317        target_os = "illumos",
318        target_os = "dragonfly",
319        target_os = "hurd",
320        target_os = "fuchsia",
321        target_os = "vxworks",
322    ))]
323    pub fn sleep_until(deadline: Instant) {
324        let Some(ts) = deadline.into_inner().into_timespec().to_timespec() else {
325            // The deadline is further in the future then can be passed to
326            // clock_nanosleep. We have to use Self::sleep instead. This might
327            // happen on 32 bit platforms, especially closer to 2038.
328            let now = Instant::now();
329            if let Some(delay) = deadline.checked_duration_since(now) {
330                Self::sleep(delay);
331            }
332            return;
333        };
334
335        unsafe {
336            // When we get interrupted (res = EINTR) call clock_nanosleep again
337            loop {
338                let res = libc::clock_nanosleep(
339                    super::time::Instant::CLOCK_ID,
340                    libc::TIMER_ABSTIME,
341                    &ts,
342                    core::ptr::null_mut(), // not required with TIMER_ABSTIME
343                );
344
345                if res == 0 {
346                    break;
347                } else {
348                    assert_eq!(
349                        res,
350                        libc::EINTR,
351                        "timespec is in range,
352                         clockid is valid and kernel should support it"
353                    );
354                }
355            }
356        }
357    }
358
359    // Any unix that does not have clock_nanosleep
360    #[cfg(not(any(
361        target_os = "freebsd",
362        target_os = "netbsd",
363        target_os = "linux",
364        target_os = "android",
365        target_os = "solaris",
366        target_os = "illumos",
367        target_os = "dragonfly",
368        target_os = "hurd",
369        target_os = "fuchsia",
370        target_os = "vxworks",
371    )))]
372    pub fn sleep_until(deadline: Instant) {
373        let now = Instant::now();
374        if let Some(delay) = deadline.checked_duration_since(now) {
375            Self::sleep(delay);
376        }
377    }
378
379    pub fn join(self) {
380        let id = self.into_id();
381        let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
382        assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
383    }
384
385    pub fn id(&self) -> libc::pthread_t {
386        self.id
387    }
388
389    pub fn into_id(self) -> libc::pthread_t {
390        ManuallyDrop::new(self).id
391    }
392}
393
394impl Drop for Thread {
395    fn drop(&mut self) {
396        let ret = unsafe { libc::pthread_detach(self.id) };
397        debug_assert_eq!(ret, 0);
398    }
399}
400
401pub(crate) fn current_os_id() -> Option<u64> {
402    // Most Unix platforms have a way to query an integer ID of the current thread, all with
403    // slightly different spellings.
404    //
405    // The OS thread ID is used rather than `pthread_self` so as to match what will be displayed
406    // for process inspection (debuggers, trace, `top`, etc.).
407    cfg_if::cfg_if! {
408        // Most platforms have a function returning a `pid_t` or int, which is an `i32`.
409        if #[cfg(any(target_os = "android", target_os = "linux"))] {
410            use crate::sys::weak::syscall;
411
412            // `libc::gettid` is only available on glibc 2.30+, but the syscall is available
413            // since Linux 2.4.11.
414            syscall!(fn gettid() -> libc::pid_t;);
415
416            // SAFETY: FFI call with no preconditions.
417            let id: libc::pid_t = unsafe { gettid() };
418            Some(id as u64)
419        } else if #[cfg(target_os = "nto")] {
420            // SAFETY: FFI call with no preconditions.
421            let id: libc::pid_t = unsafe { libc::gettid() };
422            Some(id as u64)
423        } else if #[cfg(target_os = "openbsd")] {
424            // SAFETY: FFI call with no preconditions.
425            let id: libc::pid_t = unsafe { libc::getthrid() };
426            Some(id as u64)
427        } else if #[cfg(target_os = "freebsd")] {
428            // SAFETY: FFI call with no preconditions.
429            let id: libc::c_int = unsafe { libc::pthread_getthreadid_np() };
430            Some(id as u64)
431        } else if #[cfg(target_os = "netbsd")] {
432            // SAFETY: FFI call with no preconditions.
433            let id: libc::lwpid_t = unsafe { libc::_lwp_self() };
434            Some(id as u64)
435        } else if #[cfg(any(target_os = "illumos", target_os = "solaris"))] {
436            // On Illumos and Solaris, the `pthread_t` is the same as the OS thread ID.
437            // SAFETY: FFI call with no preconditions.
438            let id: libc::pthread_t = unsafe { libc::pthread_self() };
439            Some(id as u64)
440        } else if #[cfg(target_vendor = "apple")] {
441            // Apple allows querying arbitrary thread IDs, `thread=NULL` queries the current thread.
442            let mut id = 0u64;
443            // SAFETY: `thread_id` is a valid pointer, no other preconditions.
444            let status: libc::c_int = unsafe { libc::pthread_threadid_np(0, &mut id) };
445            if status == 0 {
446                Some(id)
447            } else {
448                None
449            }
450        } else {
451            // Other platforms don't have an OS thread ID or don't have a way to access it.
452            None
453        }
454    }
455}
456
457#[cfg(any(
458    target_os = "linux",
459    target_os = "nto",
460    target_os = "solaris",
461    target_os = "illumos",
462    target_os = "vxworks",
463    target_os = "cygwin",
464    target_vendor = "apple",
465))]
466fn truncate_cstr<const MAX_WITH_NUL: usize>(cstr: &CStr) -> [libc::c_char; MAX_WITH_NUL] {
467    let mut result = [0; MAX_WITH_NUL];
468    for (src, dst) in cstr.to_bytes().iter().zip(&mut result[..MAX_WITH_NUL - 1]) {
469        *dst = *src as libc::c_char;
470    }
471    result
472}
473
474pub fn available_parallelism() -> io::Result<NonZero<usize>> {
475    cfg_if::cfg_if! {
476        if #[cfg(any(
477            target_os = "android",
478            target_os = "emscripten",
479            target_os = "fuchsia",
480            target_os = "hurd",
481            target_os = "linux",
482            target_os = "aix",
483            target_vendor = "apple",
484            target_os = "cygwin",
485        ))] {
486            #[allow(unused_assignments)]
487            #[allow(unused_mut)]
488            let mut quota = usize::MAX;
489
490            #[cfg(any(target_os = "android", target_os = "linux"))]
491            {
492                quota = cgroups::quota().max(1);
493                let mut set: libc::cpu_set_t = unsafe { mem::zeroed() };
494                unsafe {
495                    if libc::sched_getaffinity(0, size_of::<libc::cpu_set_t>(), &mut set) == 0 {
496                        let count = libc::CPU_COUNT(&set) as usize;
497                        let count = count.min(quota);
498
499                        // According to sched_getaffinity's API it should always be non-zero, but
500                        // some old MIPS kernels were buggy and zero-initialized the mask if
501                        // none was explicitly set.
502                        // In that case we use the sysconf fallback.
503                        if let Some(count) = NonZero::new(count) {
504                            return Ok(count)
505                        }
506                    }
507                }
508            }
509            match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
510                -1 => Err(io::Error::last_os_error()),
511                0 => Err(io::Error::UNKNOWN_THREAD_COUNT),
512                cpus => {
513                    let count = cpus as usize;
514                    // Cover the unusual situation where we were able to get the quota but not the affinity mask
515                    let count = count.min(quota);
516                    Ok(unsafe { NonZero::new_unchecked(count) })
517                }
518            }
519        } else if #[cfg(any(
520                   target_os = "freebsd",
521                   target_os = "dragonfly",
522                   target_os = "openbsd",
523                   target_os = "netbsd",
524               ))] {
525            use crate::ptr;
526
527            #[cfg(target_os = "freebsd")]
528            {
529                let mut set: libc::cpuset_t = unsafe { mem::zeroed() };
530                unsafe {
531                    if libc::cpuset_getaffinity(
532                        libc::CPU_LEVEL_WHICH,
533                        libc::CPU_WHICH_PID,
534                        -1,
535                        size_of::<libc::cpuset_t>(),
536                        &mut set,
537                    ) == 0 {
538                        let count = libc::CPU_COUNT(&set) as usize;
539                        if count > 0 {
540                            return Ok(NonZero::new_unchecked(count));
541                        }
542                    }
543                }
544            }
545
546            #[cfg(target_os = "netbsd")]
547            {
548                unsafe {
549                    let set = libc::_cpuset_create();
550                    if !set.is_null() {
551                        let mut count: usize = 0;
552                        if libc::pthread_getaffinity_np(libc::pthread_self(), libc::_cpuset_size(set), set) == 0 {
553                            for i in 0..libc::cpuid_t::MAX {
554                                match libc::_cpuset_isset(i, set) {
555                                    -1 => break,
556                                    0 => continue,
557                                    _ => count = count + 1,
558                                }
559                            }
560                        }
561                        libc::_cpuset_destroy(set);
562                        if let Some(count) = NonZero::new(count) {
563                            return Ok(count);
564                        }
565                    }
566                }
567            }
568
569            let mut cpus: libc::c_uint = 0;
570            let mut cpus_size = size_of_val(&cpus);
571
572            unsafe {
573                cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
574            }
575
576            // Fallback approach in case of errors or no hardware threads.
577            if cpus < 1 {
578                let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
579                let res = unsafe {
580                    libc::sysctl(
581                        mib.as_mut_ptr(),
582                        2,
583                        (&raw mut cpus) as *mut _,
584                        (&raw mut cpus_size) as *mut _,
585                        ptr::null_mut(),
586                        0,
587                    )
588                };
589
590                // Handle errors if any.
591                if res == -1 {
592                    return Err(io::Error::last_os_error());
593                } else if cpus == 0 {
594                    return Err(io::Error::UNKNOWN_THREAD_COUNT);
595                }
596            }
597
598            Ok(unsafe { NonZero::new_unchecked(cpus as usize) })
599        } else if #[cfg(target_os = "nto")] {
600            unsafe {
601                use libc::_syspage_ptr;
602                if _syspage_ptr.is_null() {
603                    Err(io::const_error!(io::ErrorKind::NotFound, "no syspage available"))
604                } else {
605                    let cpus = (*_syspage_ptr).num_cpu;
606                    NonZero::new(cpus as usize)
607                        .ok_or(io::Error::UNKNOWN_THREAD_COUNT)
608                }
609            }
610        } else if #[cfg(any(target_os = "solaris", target_os = "illumos"))] {
611            let mut cpus = 0u32;
612            if unsafe { libc::pset_info(libc::PS_MYID, core::ptr::null_mut(), &mut cpus, core::ptr::null_mut()) } != 0 {
613                return Err(io::Error::UNKNOWN_THREAD_COUNT);
614            }
615            Ok(unsafe { NonZero::new_unchecked(cpus as usize) })
616        } else if #[cfg(target_os = "haiku")] {
617            // system_info cpu_count field gets the static data set at boot time with `smp_set_num_cpus`
618            // `get_system_info` calls then `smp_get_num_cpus`
619            unsafe {
620                let mut sinfo: libc::system_info = crate::mem::zeroed();
621                let res = libc::get_system_info(&mut sinfo);
622
623                if res != libc::B_OK {
624                    return Err(io::Error::UNKNOWN_THREAD_COUNT);
625                }
626
627                Ok(NonZero::new_unchecked(sinfo.cpu_count as usize))
628            }
629        } else if #[cfg(target_os = "vxworks")] {
630            // Note: there is also `vxCpuConfiguredGet`, closer to _SC_NPROCESSORS_CONF
631            // expectations than the actual cores availability.
632            unsafe extern "C" {
633                fn vxCpuEnabledGet() -> libc::cpuset_t;
634            }
635
636            // SAFETY: `vxCpuEnabledGet` always fetches a mask with at least one bit set
637            unsafe{
638                let set = vxCpuEnabledGet();
639                Ok(NonZero::new_unchecked(set.count_ones() as usize))
640            }
641        } else {
642            // FIXME: implement on Redox, l4re
643            Err(io::const_error!(io::ErrorKind::Unsupported, "getting the number of hardware threads is not supported on the target platform"))
644        }
645    }
646}
647
648#[cfg(any(target_os = "android", target_os = "linux"))]
649mod cgroups {
650    //! Currently not covered
651    //! * cgroup v2 in non-standard mountpoints
652    //! * paths containing control characters or spaces, since those would be escaped in procfs
653    //!   output and we don't unescape
654
655    use crate::borrow::Cow;
656    use crate::ffi::OsString;
657    use crate::fs::{File, exists};
658    use crate::io::{BufRead, Read};
659    use crate::os::unix::ffi::OsStringExt;
660    use crate::path::{Path, PathBuf};
661    use crate::str::from_utf8;
662
663    #[derive(PartialEq)]
664    enum Cgroup {
665        V1,
666        V2,
667    }
668
669    /// Returns cgroup CPU quota in core-equivalents, rounded down or usize::MAX if the quota cannot
670    /// be determined or is not set.
671    pub(super) fn quota() -> usize {
672        let mut quota = usize::MAX;
673        if cfg!(miri) {
674            // Attempting to open a file fails under default flags due to isolation.
675            // And Miri does not have parallelism anyway.
676            return quota;
677        }
678
679        let _: Option<()> = try {
680            let mut buf = Vec::with_capacity(128);
681            // find our place in the cgroup hierarchy
682            File::open("/proc/self/cgroup").ok()?.read_to_end(&mut buf).ok()?;
683            let (cgroup_path, version) =
684                buf.split(|&c| c == b'\n').fold(None, |previous, line| {
685                    let mut fields = line.splitn(3, |&c| c == b':');
686                    // 2nd field is a list of controllers for v1 or empty for v2
687                    let version = match fields.nth(1) {
688                        Some(b"") => Cgroup::V2,
689                        Some(controllers)
690                            if from_utf8(controllers)
691                                .is_ok_and(|c| c.split(',').any(|c| c == "cpu")) =>
692                        {
693                            Cgroup::V1
694                        }
695                        _ => return previous,
696                    };
697
698                    // already-found v1 trumps v2 since it explicitly specifies its controllers
699                    if previous.is_some() && version == Cgroup::V2 {
700                        return previous;
701                    }
702
703                    let path = fields.last()?;
704                    // skip leading slash
705                    Some((path[1..].to_owned(), version))
706                })?;
707            let cgroup_path = PathBuf::from(OsString::from_vec(cgroup_path));
708
709            quota = match version {
710                Cgroup::V1 => quota_v1(cgroup_path),
711                Cgroup::V2 => quota_v2(cgroup_path),
712            };
713        };
714
715        quota
716    }
717
718    fn quota_v2(group_path: PathBuf) -> usize {
719        let mut quota = usize::MAX;
720
721        let mut path = PathBuf::with_capacity(128);
722        let mut read_buf = String::with_capacity(20);
723
724        // standard mount location defined in file-hierarchy(7) manpage
725        let cgroup_mount = "/sys/fs/cgroup";
726
727        path.push(cgroup_mount);
728        path.push(&group_path);
729
730        path.push("cgroup.controllers");
731
732        // skip if we're not looking at cgroup2
733        if matches!(exists(&path), Err(_) | Ok(false)) {
734            return usize::MAX;
735        };
736
737        path.pop();
738
739        let _: Option<()> = try {
740            while path.starts_with(cgroup_mount) {
741                path.push("cpu.max");
742
743                read_buf.clear();
744
745                if File::open(&path).and_then(|mut f| f.read_to_string(&mut read_buf)).is_ok() {
746                    let raw_quota = read_buf.lines().next()?;
747                    let mut raw_quota = raw_quota.split(' ');
748                    let limit = raw_quota.next()?;
749                    let period = raw_quota.next()?;
750                    match (limit.parse::<usize>(), period.parse::<usize>()) {
751                        (Ok(limit), Ok(period)) if period > 0 => {
752                            quota = quota.min(limit / period);
753                        }
754                        _ => {}
755                    }
756                }
757
758                path.pop(); // pop filename
759                path.pop(); // pop dir
760            }
761        };
762
763        quota
764    }
765
766    fn quota_v1(group_path: PathBuf) -> usize {
767        let mut quota = usize::MAX;
768        let mut path = PathBuf::with_capacity(128);
769        let mut read_buf = String::with_capacity(20);
770
771        // Hardcode commonly used locations mentioned in the cgroups(7) manpage
772        // if that doesn't work scan mountinfo and adjust `group_path` for bind-mounts
773        let mounts: &[fn(&Path) -> Option<(_, &Path)>] = &[
774            |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu"), p)),
775            |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu,cpuacct"), p)),
776            // this can be expensive on systems with tons of mountpoints
777            // but we only get to this point when /proc/self/cgroups explicitly indicated
778            // this process belongs to a cpu-controller cgroup v1 and the defaults didn't work
779            find_mountpoint,
780        ];
781
782        for mount in mounts {
783            let Some((mount, group_path)) = mount(&group_path) else { continue };
784
785            path.clear();
786            path.push(mount.as_ref());
787            path.push(&group_path);
788
789            // skip if we guessed the mount incorrectly
790            if matches!(exists(&path), Err(_) | Ok(false)) {
791                continue;
792            }
793
794            while path.starts_with(mount.as_ref()) {
795                let mut parse_file = |name| {
796                    path.push(name);
797                    read_buf.clear();
798
799                    let f = File::open(&path);
800                    path.pop(); // restore buffer before any early returns
801                    f.ok()?.read_to_string(&mut read_buf).ok()?;
802                    let parsed = read_buf.trim().parse::<usize>().ok()?;
803
804                    Some(parsed)
805                };
806
807                let limit = parse_file("cpu.cfs_quota_us");
808                let period = parse_file("cpu.cfs_period_us");
809
810                match (limit, period) {
811                    (Some(limit), Some(period)) if period > 0 => quota = quota.min(limit / period),
812                    _ => {}
813                }
814
815                path.pop();
816            }
817
818            // we passed the try_exists above so we should have traversed the correct hierarchy
819            // when reaching this line
820            break;
821        }
822
823        quota
824    }
825
826    /// Scan mountinfo for cgroup v1 mountpoint with a cpu controller
827    ///
828    /// If the cgroupfs is a bind mount then `group_path` is adjusted to skip
829    /// over the already-included prefix
830    fn find_mountpoint(group_path: &Path) -> Option<(Cow<'static, str>, &Path)> {
831        let mut reader = File::open_buffered("/proc/self/mountinfo").ok()?;
832        let mut line = String::with_capacity(256);
833        loop {
834            line.clear();
835            if reader.read_line(&mut line).ok()? == 0 {
836                break;
837            }
838
839            let line = line.trim();
840            let mut items = line.split(' ');
841
842            let sub_path = items.nth(3)?;
843            let mount_point = items.next()?;
844            let mount_opts = items.next_back()?;
845            let filesystem_type = items.nth_back(1)?;
846
847            if filesystem_type != "cgroup" || !mount_opts.split(',').any(|opt| opt == "cpu") {
848                // not a cgroup / not a cpu-controller
849                continue;
850            }
851
852            let sub_path = Path::new(sub_path).strip_prefix("/").ok()?;
853
854            if !group_path.starts_with(sub_path) {
855                // this is a bind-mount and the bound subdirectory
856                // does not contain the cgroup this process belongs to
857                continue;
858            }
859
860            let trimmed_group_path = group_path.strip_prefix(sub_path).ok()?;
861
862            return Some((Cow::Owned(mount_point.to_owned()), trimmed_group_path));
863        }
864
865        None
866    }
867}
868
869// glibc >= 2.15 has a __pthread_get_minstack() function that returns
870// PTHREAD_STACK_MIN plus bytes needed for thread-local storage.
871// We need that information to avoid blowing up when a small stack
872// is created in an application with big thread-local storage requirements.
873// See #6233 for rationale and details.
874#[cfg(all(target_os = "linux", target_env = "gnu"))]
875unsafe fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
876    // We use dlsym to avoid an ELF version dependency on GLIBC_PRIVATE. (#23628)
877    // We shouldn't really be using such an internal symbol, but there's currently
878    // no other way to account for the TLS size.
879    dlsym!(
880        fn __pthread_get_minstack(attr: *const libc::pthread_attr_t) -> libc::size_t;
881    );
882
883    match __pthread_get_minstack.get() {
884        None => libc::PTHREAD_STACK_MIN,
885        Some(f) => unsafe { f(attr) },
886    }
887}
888
889// No point in looking up __pthread_get_minstack() on non-glibc platforms.
890#[cfg(all(
891    not(all(target_os = "linux", target_env = "gnu")),
892    not(any(target_os = "netbsd", target_os = "nuttx"))
893))]
894unsafe fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
895    libc::PTHREAD_STACK_MIN
896}
897
898#[cfg(any(target_os = "netbsd", target_os = "nuttx"))]
899unsafe fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
900    static STACK: crate::sync::OnceLock<usize> = crate::sync::OnceLock::new();
901
902    *STACK.get_or_init(|| {
903        let mut stack = unsafe { libc::sysconf(libc::_SC_THREAD_STACK_MIN) };
904        if stack < 0 {
905            stack = 2048; // just a guess
906        }
907
908        stack as usize
909    })
910}
std/sys/pal/unix/thread.rs

std/sys/pal/unix/
thread.rs
