#
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
    81                    // Some libc implementations, e.g. musl, place an upper bound
    82                    // on the stack size, in which case we can only gracefully return
    83                    // an error here.
    84                    if libc::pthread_attr_setstacksize(attr.as_mut_ptr(), stack_size) != 0 {
    85                        assert_eq!(libc::pthread_attr_destroy(attr.as_mut_ptr()), 0);
    86                        drop(Box::from_raw(data));
    87                        return Err(io::const_error!(
    88                            io::ErrorKind::InvalidInput,
    89                            "invalid stack size"
    90                        ));
    91                    }
    92                }
    93            };
    94        }
    95
    96        let ret = libc::pthread_create(&mut native, attr.as_ptr(), thread_start, data as *mut _);
    97        // Note: if the thread creation fails and this assert fails, then p will
    98        // be leaked. However, an alternative design could cause double-free
    99        // which is clearly worse.
    100        assert_eq!(libc::pthread_attr_destroy(attr.as_mut_ptr()), 0);
    101
    102        return if ret != 0 {
    103            // The thread failed to start and as a result p was not consumed. Therefore, it is
    104            // safe to reconstruct the box so that it gets deallocated.
    105            drop(Box::from_raw(data));
    106            Err(io::Error::from_raw_os_error(ret))
    107        } else {
    108            Ok(Thread { id: native })
    109        };
    110
    111        extern "C" fn thread_start(data: *mut libc::c_void) -> *mut libc::c_void {
    112            unsafe {
    113                let data = Box::from_raw(data as *mut ThreadData);
    114                // Next, set up our stack overflow handler which may get triggered if we run
    115                // out of stack.
    116                let _handler = stack_overflow::Handler::new(data.name);
    117                // Finally, let's run some code.
    118                (data.f)();
    119            }
    120            ptr::null_mut()
    121        }
    122    }
    123
    124    pub fn yield_now() {
    125        let ret = unsafe { libc::sched_yield() };
    126        debug_assert_eq!(ret, 0);
    127    }
    128
    129    #[cfg(target_os = "android")]
    130    pub fn set_name(name: &CStr) {
    131        const PR_SET_NAME: libc::c_int = 15;
    132        unsafe {
    133            let res = libc::prctl(
    134                PR_SET_NAME,
    135                name.as_ptr(),
    136                0 as libc::c_ulong,
    137                0 as libc::c_ulong,
    138                0 as libc::c_ulong,
    139            );
    140            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
    141            debug_assert_eq!(res, 0);
    142        }
    143    }
    144
    145    #[cfg(any(
    146        target_os = "linux",
    147        target_os = "freebsd",
    148        target_os = "dragonfly",
    149        target_os = "nuttx",
    150        target_os = "cygwin"
    151    ))]
    152    pub fn set_name(name: &CStr) {
    153        unsafe {
    154            cfg_if::cfg_if! {
    155                if #[cfg(any(target_os = "linux", target_os = "cygwin"))] {
    156                    // Linux and Cygwin limits the allowed length of the name.
    157                    const TASK_COMM_LEN: usize = 16;
    158                    let name = truncate_cstr::<{ TASK_COMM_LEN }>(name);
    159                } else {
    160                    // FreeBSD, DragonFly BSD and NuttX do not enforce length limits.
    161                }
    162            };
    163            // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20 for Linux,
    164            // FreeBSD 12.2 and 13.0, and DragonFly BSD 6.0.
    165            let res = libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
    166            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
    167            debug_assert_eq!(res, 0);
    168        }
    169    }
    170
    171    #[cfg(target_os = "openbsd")]
    172    pub fn set_name(name: &CStr) {
    173        unsafe {
    174            libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
    175        }
    176    }
    177
    178    #[cfg(target_vendor = "apple")]
    179    pub fn set_name(name: &CStr) {
    180        unsafe {
    181            let name = truncate_cstr::<{ libc::MAXTHREADNAMESIZE }>(name);
    182            let res = libc::pthread_setname_np(name.as_ptr());
    183            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
    184            debug_assert_eq!(res, 0);
    185        }
    186    }
    187
    188    #[cfg(target_os = "netbsd")]
    189    pub fn set_name(name: &CStr) {
    190        unsafe {
    191            let res = libc::pthread_setname_np(
    192                libc::pthread_self(),
    193                c"%s".as_ptr(),
    194                name.as_ptr() as *mut libc::c_void,
    195            );
    196            debug_assert_eq!(res, 0);
    197        }
    198    }
    199
    200    #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
    201    pub fn set_name(name: &CStr) {
    202        weak!(
    203            fn pthread_setname_np(
    204                thread: libc::pthread_t,
    205                name: *const libc::c_char,
    206            ) -> libc::c_int;
    207        );
    208
    209        if let Some(f) = pthread_setname_np.get() {
    210            #[cfg(target_os = "nto")]
    211            const THREAD_NAME_MAX: usize = libc::_NTO_THREAD_NAME_MAX as usize;
    212            #[cfg(any(target_os = "solaris", target_os = "illumos"))]
    213            const THREAD_NAME_MAX: usize = 32;
    214
    215            let name = truncate_cstr::<{ THREAD_NAME_MAX }>(name);
    216            let res = unsafe { f(libc::pthread_self(), name.as_ptr()) };
    217            debug_assert_eq!(res, 0);
    218        }
    219    }
    220
    221    #[cfg(target_os = "fuchsia")]
    222    pub fn set_name(name: &CStr) {
    223        use super::fuchsia::*;
    224        unsafe {
    225            zx_object_set_property(
    226                zx_thread_self(),
    227                ZX_PROP_NAME,
    228                name.as_ptr() as *const libc::c_void,
    229                name.to_bytes().len(),
    230            );
    231        }
    232    }
    233
    234    #[cfg(target_os = "haiku")]
    235    pub fn set_name(name: &CStr) {
    236        unsafe {
    237            let thread_self = libc::find_thread(ptr::null_mut());
    238            let res = libc::rename_thread(thread_self, name.as_ptr());
    239            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
    240            debug_assert_eq!(res, libc::B_OK);
    241        }
    242    }
    243
    244    #[cfg(target_os = "vxworks")]
    245    pub fn set_name(name: &CStr) {
    246        let mut name = truncate_cstr::<{ (libc::VX_TASK_RENAME_LENGTH - 1) as usize }>(name);
    247        let res = unsafe { libc::taskNameSet(libc::taskIdSelf(), name.as_mut_ptr()) };
    248        debug_assert_eq!(res, libc::OK);
    249    }
    250
    251    #[cfg(any(
    252        target_env = "newlib",
    253        target_os = "l4re",
    254        target_os = "emscripten",
    255        target_os = "redox",
    256        target_os = "hurd",
    257        target_os = "aix",
    258    ))]
    259    pub fn set_name(_name: &CStr) {
    260        // Newlib and Emscripten have no way to set a thread name.
    261    }
    262
    263    #[cfg(not(target_os = "espidf"))]
    264    pub fn sleep(dur: Duration) {
    265        let mut secs = dur.as_secs();
    266        let mut nsecs = dur.subsec_nanos() as _;
    267
    268        // If we're awoken with a signal then the return value will be -1 and
    269        // nanosleep will fill in `ts` with the remaining time.
    270        unsafe {
    271            while secs > 0 || nsecs > 0 {
    272                let mut ts = libc::timespec {
    273                    tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
    274                    tv_nsec: nsecs,
    275                };
    276                secs -= ts.tv_sec as u64;
    277                let ts_ptr = &raw mut ts;
    278                if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
    279                    assert_eq!(os::errno(), libc::EINTR);
    280                    secs += ts.tv_sec as u64;
    281                    nsecs = ts.tv_nsec;
    282                } else {
    283                    nsecs = 0;
    284                }
    285            }
    286        }
    287    }
    288
    289    #[cfg(target_os = "espidf")]
    290    pub fn sleep(dur: Duration) {
    291        // ESP-IDF does not have `nanosleep`, so we use `usleep` instead.
    292        // As per the documentation of `usleep`, it is expected to support
    293        // sleep times as big as at least up to 1 second.
    294        //
    295        // ESP-IDF does support almost up to `u32::MAX`, but due to a potential integer overflow in its
    296        // `usleep` implementation
    297        // (https://github.com/espressif/esp-idf/blob/d7ca8b94c852052e3bc33292287ef4dd62c9eeb1/components/newlib/time.c#L210),
    298        // we limit the sleep time to the maximum one that would not cause the underlying `usleep` implementation to overflow
    299        // (`portTICK_PERIOD_MS` can be anything between 1 to 1000, and is 10 by default).
    300        const MAX_MICROS: u32 = u32::MAX - 1_000_000 - 1;
    301
    302        // Add any nanoseconds smaller than a microsecond as an extra microsecond
    303        // so as to comply with the `std::thread::sleep` contract which mandates
    304        // implementations to sleep for _at least_ the provided `dur`.
    305        // We can't overflow `micros` as it is a `u128`, while `Duration` is a pair of
    306        // (`u64` secs, `u32` nanos), where the nanos are strictly smaller than 1 second
    307        // (i.e. < 1_000_000_000)
    308        let mut micros = dur.as_micros() + if dur.subsec_nanos() % 1_000 > 0 { 1 } else { 0 };
    309
    310        while micros > 0 {
    311            let st = if micros > MAX_MICROS as u128 { MAX_MICROS } else { micros as u32 };
    312            unsafe {
    313                libc::usleep(st);
    314            }
    315
    316            micros -= st as u128;
    317        }
    318    }
    319
    320    // Any unix that has clock_nanosleep
    321    // If this list changes update the MIRI chock_nanosleep shim
    322    #[cfg(any(
    323        target_os = "freebsd",
    324        target_os = "netbsd",
    325        target_os = "linux",
    326        target_os = "android",
    327        target_os = "solaris",
    328        target_os = "illumos",
    329        target_os = "dragonfly",
    330        target_os = "hurd",
    331        target_os = "fuchsia",
    332        target_os = "vxworks",
    333    ))]
    334    pub fn sleep_until(deadline: Instant) {
    335        let Some(ts) = deadline.into_inner().into_timespec().to_timespec() else {
    336            // The deadline is further in the future then can be passed to
    337            // clock_nanosleep. We have to use Self::sleep instead. This might
    338            // happen on 32 bit platforms, especially closer to 2038.
    339            let now = Instant::now();
    340            if let Some(delay) = deadline.checked_duration_since(now) {
    341                Self::sleep(delay);
    342            }
    343            return;
    344        };
    345
    346        unsafe {
    347            // When we get interrupted (res = EINTR) call clock_nanosleep again
    348            loop {
    349                let res = libc::clock_nanosleep(
    350                    super::time::Instant::CLOCK_ID,
    351                    libc::TIMER_ABSTIME,
    352                    &ts,
    353                    core::ptr::null_mut(), // not required with TIMER_ABSTIME
    354                );
    355
    356                if res == 0 {
    357                    break;
    358                } else {
    359                    assert_eq!(
    360                        res,
    361                        libc::EINTR,
    362                        "timespec is in range,
    363                         clockid is valid and kernel should support it"
    364                    );
    365                }
    366            }
    367        }
    368    }
    369
    370    // Any unix that does not have clock_nanosleep
    371    #[cfg(not(any(
    372        target_os = "freebsd",
    373        target_os = "netbsd",
    374        target_os = "linux",
    375        target_os = "android",
    376        target_os = "solaris",
    377        target_os = "illumos",
    378        target_os = "dragonfly",
    379        target_os = "hurd",
    380        target_os = "fuchsia",
    381        target_os = "vxworks",
    382    )))]
    383    pub fn sleep_until(deadline: Instant) {
    384        let now = Instant::now();
    385        if let Some(delay) = deadline.checked_duration_since(now) {
    386            Self::sleep(delay);
    387        }
    388    }
    389
    390    pub fn join(self) {
    391        let id = self.into_id();
    392        let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
    393        assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
    394    }
    395
    396    pub fn id(&self) -> libc::pthread_t {
    397        self.id
    398    }
    399
    400    pub fn into_id(self) -> libc::pthread_t {
    401        ManuallyDrop::new(self).id
    402    }
    403}
    404
    405impl Drop for Thread {
    406    fn drop(&mut self) {
    407        let ret = unsafe { libc::pthread_detach(self.id) };
    408        debug_assert_eq!(ret, 0);
    409    }
    410}
    411
    412pub(crate) fn current_os_id() -> Option<u64> {
    413    // Most Unix platforms have a way to query an integer ID of the current thread, all with
    414    // slightly different spellings.
    415    //
    416    // The OS thread ID is used rather than `pthread_self` so as to match what will be displayed
    417    // for process inspection (debuggers, trace, `top`, etc.).
    418    cfg_if::cfg_if! {
    419        // Most platforms have a function returning a `pid_t` or int, which is an `i32`.
    420        if #[cfg(any(target_os = "android", target_os = "linux"))] {
    421            use crate::sys::weak::syscall;
    422
    423            // `libc::gettid` is only available on glibc 2.30+, but the syscall is available
    424            // since Linux 2.4.11.
    425            syscall!(fn gettid() -> libc::pid_t;);
    426
    427            // SAFETY: FFI call with no preconditions.
    428            let id: libc::pid_t = unsafe { gettid() };
    429            Some(id as u64)
    430        } else if #[cfg(target_os = "nto")] {
    431            // SAFETY: FFI call with no preconditions.
    432            let id: libc::pid_t = unsafe { libc::gettid() };
    433            Some(id as u64)
    434        } else if #[cfg(target_os = "openbsd")] {
    435            // SAFETY: FFI call with no preconditions.
    436            let id: libc::pid_t = unsafe { libc::getthrid() };
    437            Some(id as u64)
    438        } else if #[cfg(target_os = "freebsd")] {
    439            // SAFETY: FFI call with no preconditions.
    440            let id: libc::c_int = unsafe { libc::pthread_getthreadid_np() };
    441            Some(id as u64)
    442        } else if #[cfg(target_os = "netbsd")] {
    443            // SAFETY: FFI call with no preconditions.
    444            let id: libc::lwpid_t = unsafe { libc::_lwp_self() };
    445            Some(id as u64)
    446        } else if #[cfg(any(target_os = "illumos", target_os = "solaris"))] {
    447            // On Illumos and Solaris, the `pthread_t` is the same as the OS thread ID.
    448            // SAFETY: FFI call with no preconditions.
    449            let id: libc::pthread_t = unsafe { libc::pthread_self() };
    450            Some(id as u64)
    451        } else if #[cfg(target_vendor = "apple")] {
    452            // Apple allows querying arbitrary thread IDs, `thread=NULL` queries the current thread.
    453            let mut id = 0u64;
    454            // SAFETY: `thread_id` is a valid pointer, no other preconditions.
    455            let status: libc::c_int = unsafe { libc::pthread_threadid_np(0, &mut id) };
    456            if status == 0 {
    457                Some(id)
    458            } else {
    459                None
    460            }
    461        } else {
    462            // Other platforms don't have an OS thread ID or don't have a way to access it.
    463            None
    464        }
    465    }
    466}
    467
    468#[cfg(any(
    469    target_os = "linux",
    470    target_os = "nto",
    471    target_os = "solaris",
    472    target_os = "illumos",
    473    target_os = "vxworks",
    474    target_os = "cygwin",
    475    target_vendor = "apple",
    476))]
    477fn truncate_cstr<const MAX_WITH_NUL: usize>(cstr: &CStr) -> [libc::c_char; MAX_WITH_NUL] {
    478    let mut result = [0; MAX_WITH_NUL];
    479    for (src, dst) in cstr.to_bytes().iter().zip(&mut result[..MAX_WITH_NUL - 1]) {
    480        *dst = *src as libc::c_char;
    481    }
    482    result
    483}
    484
    485pub fn available_parallelism() -> io::Result<NonZero<usize>> {
    486    cfg_if::cfg_if! {
    487        if #[cfg(any(
    488            target_os = "android",
    489            target_os = "emscripten",
    490            target_os = "fuchsia",
    491            target_os = "hurd",
    492            target_os = "linux",
    493            target_os = "aix",
    494            target_vendor = "apple",
    495            target_os = "cygwin",
    496        ))] {
    497            #[allow(unused_assignments)]
    498            #[allow(unused_mut)]
    499            let mut quota = usize::MAX;
    500
    501            #[cfg(any(target_os = "android", target_os = "linux"))]
    502            {
    503                quota = cgroups::quota().max(1);
    504                let mut set: libc::cpu_set_t = unsafe { mem::zeroed() };
    505                unsafe {
    506                    if libc::sched_getaffinity(0, size_of::<libc::cpu_set_t>(), &mut set) == 0 {
    507                        let count = libc::CPU_COUNT(&set) as usize;
    508                        let count = count.min(quota);
    509
    510                        // According to sched_getaffinity's API it should always be non-zero, but
    511                        // some old MIPS kernels were buggy and zero-initialized the mask if
    512                        // none was explicitly set.
    513                        // In that case we use the sysconf fallback.
    514                        if let Some(count) = NonZero::new(count) {
    515                            return Ok(count)
    516                        }
    517                    }
    518                }
    519            }
    520            match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
    521                -1 => Err(io::Error::last_os_error()),
    522                0 => Err(io::Error::UNKNOWN_THREAD_COUNT),
    523                cpus => {
    524                    let count = cpus as usize;
    525                    // Cover the unusual situation where we were able to get the quota but not the affinity mask
    526                    let count = count.min(quota);
    527                    Ok(unsafe { NonZero::new_unchecked(count) })
    528                }
    529            }
    530        } else if #[cfg(any(
    531                   target_os = "freebsd",
    532                   target_os = "dragonfly",
    533                   target_os = "openbsd",
    534                   target_os = "netbsd",
    535               ))] {
    536            use crate::ptr;
    537
    538            #[cfg(target_os = "freebsd")]
    539            {
    540                let mut set: libc::cpuset_t = unsafe { mem::zeroed() };
    541                unsafe {
    542                    if libc::cpuset_getaffinity(
    543                        libc::CPU_LEVEL_WHICH,
    544                        libc::CPU_WHICH_PID,
    545                        -1,
    546                        size_of::<libc::cpuset_t>(),
    547                        &mut set,
    548                    ) == 0 {
    549                        let count = libc::CPU_COUNT(&set) as usize;
    550                        if count > 0 {
    551                            return Ok(NonZero::new_unchecked(count));
    552                        }
    553                    }
    554                }
    555            }
    556
    557            #[cfg(target_os = "netbsd")]
    558            {
    559                unsafe {
    560                    let set = libc::_cpuset_create();
    561                    if !set.is_null() {
    562                        let mut count: usize = 0;
    563                        if libc::pthread_getaffinity_np(libc::pthread_self(), libc::_cpuset_size(set), set) == 0 {
    564                            for i in 0..libc::cpuid_t::MAX {
    565                                match libc::_cpuset_isset(i, set) {
    566                                    -1 => break,
    567                                    0 => continue,
    568                                    _ => count = count + 1,
    569                                }
    570                            }
    571                        }
    572                        libc::_cpuset_destroy(set);
    573                        if let Some(count) = NonZero::new(count) {
    574                            return Ok(count);
    575                        }
    576                    }
    577                }
    578            }
    579
    580            let mut cpus: libc::c_uint = 0;
    581            let mut cpus_size = size_of_val(&cpus);
    582
    583            unsafe {
    584                cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
    585            }
    586
    587            // Fallback approach in case of errors or no hardware threads.
    588            if cpus < 1 {
    589                let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
    590                let res = unsafe {
    591                    libc::sysctl(
    592                        mib.as_mut_ptr(),
    593                        2,
    594                        (&raw mut cpus) as *mut _,
    595                        (&raw mut cpus_size) as *mut _,
    596                        ptr::null_mut(),
    597                        0,
    598                    )
    599                };
    600
    601                // Handle errors if any.
    602                if res == -1 {
    603                    return Err(io::Error::last_os_error());
    604                } else if cpus == 0 {
    605                    return Err(io::Error::UNKNOWN_THREAD_COUNT);
    606                }
    607            }
    608
    609            Ok(unsafe { NonZero::new_unchecked(cpus as usize) })
    610        } else if #[cfg(target_os = "nto")] {
    611            unsafe {
    612                use libc::_syspage_ptr;
    613                if _syspage_ptr.is_null() {
    614                    Err(io::const_error!(io::ErrorKind::NotFound, "no syspage available"))
    615                } else {
    616                    let cpus = (*_syspage_ptr).num_cpu;
    617                    NonZero::new(cpus as usize)
    618                        .ok_or(io::Error::UNKNOWN_THREAD_COUNT)
    619                }
    620            }
    621        } else if #[cfg(any(target_os = "solaris", target_os = "illumos"))] {
    622            let mut cpus = 0u32;
    623            if unsafe { libc::pset_info(libc::PS_MYID, core::ptr::null_mut(), &mut cpus, core::ptr::null_mut()) } != 0 {
    624                return Err(io::Error::UNKNOWN_THREAD_COUNT);
    625            }
    626            Ok(unsafe { NonZero::new_unchecked(cpus as usize) })
    627        } else if #[cfg(target_os = "haiku")] {
    628            // system_info cpu_count field gets the static data set at boot time with `smp_set_num_cpus`
    629            // `get_system_info` calls then `smp_get_num_cpus`
    630            unsafe {
    631                let mut sinfo: libc::system_info = crate::mem::zeroed();
    632                let res = libc::get_system_info(&mut sinfo);
    633
    634                if res != libc::B_OK {
    635                    return Err(io::Error::UNKNOWN_THREAD_COUNT);
    636                }
    637
    638                Ok(NonZero::new_unchecked(sinfo.cpu_count as usize))
    639            }
    640        } else if #[cfg(target_os = "vxworks")] {
    641            // Note: there is also `vxCpuConfiguredGet`, closer to _SC_NPROCESSORS_CONF
    642            // expectations than the actual cores availability.
    643            unsafe extern "C" {
    644                fn vxCpuEnabledGet() -> libc::cpuset_t;
    645            }
    646
    647            // SAFETY: `vxCpuEnabledGet` always fetches a mask with at least one bit set
    648            unsafe{
    649                let set = vxCpuEnabledGet();
    650                Ok(NonZero::new_unchecked(set.count_ones() as usize))
    651            }
    652        } else {
    653            // FIXME: implement on Redox, l4re
    654            Err(io::const_error!(io::ErrorKind::Unsupported, "getting the number of hardware threads is not supported on the target platform"))
    655        }
    656    }
    657}
    658
    659#[cfg(any(target_os = "android", target_os = "linux"))]
    660mod cgroups {
    661    //! Currently not covered
    662    //! * cgroup v2 in non-standard mountpoints
    663    //! * paths containing control characters or spaces, since those would be escaped in procfs
    664    //!   output and we don't unescape
    665
    666    use crate::borrow::Cow;
    667    use crate::ffi::OsString;
    668    use crate::fs::{File, exists};
    669    use crate::io::{BufRead, Read};
    670    use crate::os::unix::ffi::OsStringExt;
    671    use crate::path::{Path, PathBuf};
    672    use crate::str::from_utf8;
    673
    674    #[derive(PartialEq)]
    675    enum Cgroup {
    676        V1,
    677        V2,
    678    }
    679
    680    /// Returns cgroup CPU quota in core-equivalents, rounded down or usize::MAX if the quota cannot
    681    /// be determined or is not set.
    682    pub(super) fn quota() -> usize {
    683        let mut quota = usize::MAX;
    684        if cfg!(miri) {
    685            // Attempting to open a file fails under default flags due to isolation.
    686            // And Miri does not have parallelism anyway.
    687            return quota;
    688        }
    689
    690        let _: Option<()> = try {
    691            let mut buf = Vec::with_capacity(128);
    692            // find our place in the cgroup hierarchy
    693            File::open("/proc/self/cgroup").ok()?.read_to_end(&mut buf).ok()?;
    694            let (cgroup_path, version) =
    695                buf.split(|&c| c == b'\n').fold(None, |previous, line| {
    696                    let mut fields = line.splitn(3, |&c| c == b':');
    697                    // 2nd field is a list of controllers for v1 or empty for v2
    698                    let version = match fields.nth(1) {
    699                        Some(b"") => Cgroup::V2,
    700                        Some(controllers)
    701                            if from_utf8(controllers)
    702                                .is_ok_and(|c| c.split(',').any(|c| c == "cpu")) =>
    703                        {
    704                            Cgroup::V1
    705                        }
    706                        _ => return previous,
    707                    };
    708
    709                    // already-found v1 trumps v2 since it explicitly specifies its controllers
    710                    if previous.is_some() && version == Cgroup::V2 {
    711                        return previous;
    712                    }
    713
    714                    let path = fields.last()?;
    715                    // skip leading slash
    716                    Some((path[1..].to_owned(), version))
    717                })?;
    718            let cgroup_path = PathBuf::from(OsString::from_vec(cgroup_path));
    719
    720            quota = match version {
    721                Cgroup::V1 => quota_v1(cgroup_path),
    722                Cgroup::V2 => quota_v2(cgroup_path),
    723            };
    724        };
    725
    726        quota
    727    }
    728
    729    fn quota_v2(group_path: PathBuf) -> usize {
    730        let mut quota = usize::MAX;
    731
    732        let mut path = PathBuf::with_capacity(128);
    733        let mut read_buf = String::with_capacity(20);
    734
    735        // standard mount location defined in file-hierarchy(7) manpage
    736        let cgroup_mount = "/sys/fs/cgroup";
    737
    738        path.push(cgroup_mount);
    739        path.push(&group_path);
    740
    741        path.push("cgroup.controllers");
    742
    743        // skip if we're not looking at cgroup2
    744        if matches!(exists(&path), Err(_) | Ok(false)) {
    745            return usize::MAX;
    746        };
    747
    748        path.pop();
    749
    750        let _: Option<()> = try {
    751            while path.starts_with(cgroup_mount) {
    752                path.push("cpu.max");
    753
    754                read_buf.clear();
    755
    756                if File::open(&path).and_then(|mut f| f.read_to_string(&mut read_buf)).is_ok() {
    757                    let raw_quota = read_buf.lines().next()?;
    758                    let mut raw_quota = raw_quota.split(' ');
    759                    let limit = raw_quota.next()?;
    760                    let period = raw_quota.next()?;
    761                    match (limit.parse::<usize>(), period.parse::<usize>()) {
    762                        (Ok(limit), Ok(period)) if period > 0 => {
    763                            quota = quota.min(limit / period);
    764                        }
    765                        _ => {}
    766                    }
    767                }
    768
    769                path.pop(); // pop filename
    770                path.pop(); // pop dir
    771            }
    772        };
    773
    774        quota
    775    }
    776
    777    fn quota_v1(group_path: PathBuf) -> usize {
    778        let mut quota = usize::MAX;
    779        let mut path = PathBuf::with_capacity(128);
    780        let mut read_buf = String::with_capacity(20);
    781
    782        // Hardcode commonly used locations mentioned in the cgroups(7) manpage
    783        // if that doesn't work scan mountinfo and adjust `group_path` for bind-mounts
    784        let mounts: &[fn(&Path) -> Option<(_, &Path)>] = &[
    785            |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu"), p)),
    786            |p| Some((Cow::Borrowed("/sys/fs/cgroup/cpu,cpuacct"), p)),
    787            // this can be expensive on systems with tons of mountpoints
    788            // but we only get to this point when /proc/self/cgroups explicitly indicated
    789            // this process belongs to a cpu-controller cgroup v1 and the defaults didn't work
    790            find_mountpoint,
    791        ];
    792
    793        for mount in mounts {
    794            let Some((mount, group_path)) = mount(&group_path) else { continue };
    795
    796            path.clear();
    797            path.push(mount.as_ref());
    798            path.push(&group_path);
    799
    800            // skip if we guessed the mount incorrectly
    801            if matches!(exists(&path), Err(_) | Ok(false)) {
    802                continue;
    803            }
    804
    805            while path.starts_with(mount.as_ref()) {
    806                let mut parse_file = |name| {
    807                    path.push(name);
    808                    read_buf.clear();
    809
    810                    let f = File::open(&path);
    811                    path.pop(); // restore buffer before any early returns
    812                    f.ok()?.read_to_string(&mut read_buf).ok()?;
    813                    let parsed = read_buf.trim().parse::<usize>().ok()?;
    814
    815                    Some(parsed)
    816                };
    817
    818                let limit = parse_file("cpu.cfs_quota_us");
    819                let period = parse_file("cpu.cfs_period_us");
    820
    821                match (limit, period) {
    822                    (Some(limit), Some(period)) if period > 0 => quota = quota.min(limit / period),
    823                    _ => {}
    824                }
    825
    826                path.pop();
    827            }
    828
    829            // we passed the try_exists above so we should have traversed the correct hierarchy
    830            // when reaching this line
    831            break;
    832        }
    833
    834        quota
    835    }
    836
    837    /// Scan mountinfo for cgroup v1 mountpoint with a cpu controller
    838    ///
    839    /// If the cgroupfs is a bind mount then `group_path` is adjusted to skip
    840    /// over the already-included prefix
    841    fn find_mountpoint(group_path: &Path) -> Option<(Cow<'static, str>, &Path)> {
    842        let mut reader = File::open_buffered("/proc/self/mountinfo").ok()?;
    843        let mut line = String::with_capacity(256);
    844        loop {
    845            line.clear();
    846            if reader.read_line(&mut line).ok()? == 0 {
    847                break;
    848            }
    849
    850            let line = line.trim();
    851            let mut items = line.split(' ');
    852
    853            let sub_path = items.nth(3)?;
    854            let mount_point = items.next()?;
    855            let mount_opts = items.next_back()?;
    856            let filesystem_type = items.nth_back(1)?;
    857
    858            if filesystem_type != "cgroup" || !mount_opts.split(',').any(|opt| opt == "cpu") {
    859                // not a cgroup / not a cpu-controller
    860                continue;
    861            }
    862
    863            let sub_path = Path::new(sub_path).strip_prefix("/").ok()?;
    864
    865            if !group_path.starts_with(sub_path) {
    866                // this is a bind-mount and the bound subdirectory
    867                // does not contain the cgroup this process belongs to
    868                continue;
    869            }
    870
    871            let trimmed_group_path = group_path.strip_prefix(sub_path).ok()?;
    872
    873            return Some((Cow::Owned(mount_point.to_owned()), trimmed_group_path));
    874        }
    875
    876        None
    877    }
    878}
    879
    880// glibc >= 2.15 has a __pthread_get_minstack() function that returns
    881// PTHREAD_STACK_MIN plus bytes needed for thread-local storage.
    882// We need that information to avoid blowing up when a small stack
    883// is created in an application with big thread-local storage requirements.
    884// See #6233 for rationale and details.
    885#[cfg(all(target_os = "linux", target_env = "gnu"))]
    886unsafe fn min_stack_size(attr: *const libc::pthread_attr_t) -> usize {
    887    // We use dlsym to avoid an ELF version dependency on GLIBC_PRIVATE. (#23628)
    888    // We shouldn't really be using such an internal symbol, but there's currently
    889    // no other way to account for the TLS size.
    890    dlsym!(
    891        fn __pthread_get_minstack(attr: *const libc::pthread_attr_t) -> libc::size_t;
    892    );
    893
    894    match __pthread_get_minstack.get() {
    895        None => libc::PTHREAD_STACK_MIN,
    896        Some(f) => unsafe { f(attr) },
    897    }
    898}
    899
    900// No point in looking up __pthread_get_minstack() on non-glibc platforms.
    901#[cfg(all(
    902    not(all(target_os = "linux", target_env = "gnu")),
    903    not(any(target_os = "netbsd", target_os = "nuttx"))
    904))]
    905unsafe fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
    906    libc::PTHREAD_STACK_MIN
    907}
    908
    909#[cfg(any(target_os = "netbsd", target_os = "nuttx"))]
    910unsafe fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
    911    static STACK: crate::sync::OnceLock<usize> = crate::sync::OnceLock::new();
    912
    913    *STACK.get_or_init(|| {
    914        let mut stack = unsafe { libc::sysconf(libc::_SC_THREAD_STACK_MIN) };
    915        if stack < 0 {
    916            stack = 2048; // just a guess
    917        }
    918
    919        stack as usize
    920    })
    921}