1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
//! Execution scheduling
//!
//! See Also
//! [sched.h](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sched.h.html)
use crate::{Errno, Result};

#[cfg(linux_android)]
pub use self::sched_linux_like::*;

#[cfg(linux_android)]
mod sched_linux_like {
    use crate::errno::Errno;
    use crate::unistd::Pid;
    use crate::Result;
    use libc::{self, c_int, c_void};
    use std::mem;
    use std::option::Option;
    use std::os::unix::io::{AsFd, AsRawFd};

    // For some functions taking with a parameter of type CloneFlags,
    // only a subset of these flags have an effect.
    libc_bitflags! {
        /// Options for use with [`clone`]
        pub struct CloneFlags: c_int {
            /// The calling process and the child process run in the same
            /// memory space.
            CLONE_VM;
            /// The caller and the child process share the same  filesystem
            /// information.
            CLONE_FS;
            /// The calling process and the child process share the same file
            /// descriptor table.
            CLONE_FILES;
            /// The calling process and the child process share the same table
            /// of signal handlers.
            CLONE_SIGHAND;
            /// If the calling process is being traced, then trace the child
            /// also.
            CLONE_PTRACE;
            /// The execution of the calling process is suspended until the
            /// child releases its virtual memory resources via a call to
            /// execve(2) or _exit(2) (as with vfork(2)).
            CLONE_VFORK;
            /// The parent of the new child  (as returned by getppid(2))
            /// will be the same as that of the calling process.
            CLONE_PARENT;
            /// The child is placed in the same thread group as the calling
            /// process.
            CLONE_THREAD;
            /// The cloned child is started in a new mount namespace.
            CLONE_NEWNS;
            /// The child and the calling process share a single list of System
            /// V semaphore adjustment values
            CLONE_SYSVSEM;
            // Not supported by Nix due to lack of varargs support in Rust FFI
            // CLONE_SETTLS;
            // Not supported by Nix due to lack of varargs support in Rust FFI
            // CLONE_PARENT_SETTID;
            // Not supported by Nix due to lack of varargs support in Rust FFI
            // CLONE_CHILD_CLEARTID;
            /// Unused since Linux 2.6.2
            #[deprecated(since = "0.23.0", note = "Deprecated by Linux 2.6.2")]
            CLONE_DETACHED;
            /// A tracing process cannot force `CLONE_PTRACE` on this child
            /// process.
            CLONE_UNTRACED;
            // Not supported by Nix due to lack of varargs support in Rust FFI
            // CLONE_CHILD_SETTID;
            /// Create the process in a new cgroup namespace.
            CLONE_NEWCGROUP;
            /// Create the process in a new UTS namespace.
            CLONE_NEWUTS;
            /// Create the process in a new IPC namespace.
            CLONE_NEWIPC;
            /// Create the process in a new user namespace.
            CLONE_NEWUSER;
            /// Create the process in a new PID namespace.
            CLONE_NEWPID;
            /// Create the process in a new network namespace.
            CLONE_NEWNET;
            /// The new process shares an I/O context with the calling process.
            CLONE_IO;
        }
    }

    /// Type for the function executed by [`clone`].
    pub type CloneCb<'a> = Box<dyn FnMut() -> isize + 'a>;

    /// `clone` create a child process
    /// ([`clone(2)`](https://man7.org/linux/man-pages/man2/clone.2.html))
    ///
    /// `stack` is a reference to an array which will hold the stack of the new
    /// process.  Unlike when calling `clone(2)` from C, the provided stack
    /// address need not be the highest address of the region.  Nix will take
    /// care of that requirement.  The user only needs to provide a reference to
    /// a normally allocated buffer.
    ///
    /// # Safety
    ///
    /// Because `clone` creates a child process with its stack located in
    /// `stack` without specifying the size of the stack, special care must be
    /// taken to ensure that the child process does not overflow the provided
    /// stack space.
    ///
    /// See [`fork`](crate::unistd::fork) for additional safety concerns related
    /// to executing child processes.
    pub unsafe fn clone(
        mut cb: CloneCb,
        stack: &mut [u8],
        flags: CloneFlags,
        signal: Option<c_int>,
    ) -> Result<Pid> {
        extern "C" fn callback(data: *mut CloneCb) -> c_int {
            let cb: &mut CloneCb = unsafe { &mut *data };
            (*cb)() as c_int
        }

        let combined = flags.bits() | signal.unwrap_or(0);
        let res = unsafe {
            let ptr = stack.as_mut_ptr().add(stack.len());
            let ptr_aligned = ptr.sub(ptr as usize % 16);
            libc::clone(
                mem::transmute(
                    callback
                        as extern "C" fn(*mut Box<dyn FnMut() -> isize>) -> i32,
                ),
                ptr_aligned as *mut c_void,
                combined,
                &mut cb as *mut _ as *mut c_void,
            )
        };

        Errno::result(res).map(Pid::from_raw)
    }

    /// disassociate parts of the process execution context
    ///
    /// See also [unshare(2)](https://man7.org/linux/man-pages/man2/unshare.2.html)
    pub fn unshare(flags: CloneFlags) -> Result<()> {
        let res = unsafe { libc::unshare(flags.bits()) };

        Errno::result(res).map(drop)
    }

    /// reassociate thread with a namespace
    ///
    /// See also [setns(2)](https://man7.org/linux/man-pages/man2/setns.2.html)
    pub fn setns<Fd: AsFd>(fd: Fd, nstype: CloneFlags) -> Result<()> {
        let res = unsafe { libc::setns(fd.as_fd().as_raw_fd(), nstype.bits()) };

        Errno::result(res).map(drop)
    }
}

#[cfg(any(linux_android, freebsdlike))]
pub use self::sched_affinity::*;

#[cfg(any(linux_android, freebsdlike))]
mod sched_affinity {
    use crate::errno::Errno;
    use crate::unistd::Pid;
    use crate::Result;
    use std::mem;

    /// CpuSet represent a bit-mask of CPUs.
    /// CpuSets are used by sched_setaffinity and
    /// sched_getaffinity for example.
    ///
    /// This is a wrapper around `libc::cpu_set_t`.
    #[repr(transparent)]
    #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
    pub struct CpuSet {
        #[cfg(not(target_os = "freebsd"))]
        cpu_set: libc::cpu_set_t,
        #[cfg(target_os = "freebsd")]
        cpu_set: libc::cpuset_t,
    }

    impl CpuSet {
        /// Create a new and empty CpuSet.
        pub fn new() -> CpuSet {
            CpuSet {
                cpu_set: unsafe { mem::zeroed() },
            }
        }

        /// Test to see if a CPU is in the CpuSet.
        /// `field` is the CPU id to test
        pub fn is_set(&self, field: usize) -> Result<bool> {
            if field >= CpuSet::count() {
                Err(Errno::EINVAL)
            } else {
                Ok(unsafe { libc::CPU_ISSET(field, &self.cpu_set) })
            }
        }

        /// Add a CPU to CpuSet.
        /// `field` is the CPU id to add
        pub fn set(&mut self, field: usize) -> Result<()> {
            if field >= CpuSet::count() {
                Err(Errno::EINVAL)
            } else {
                unsafe {
                    libc::CPU_SET(field, &mut self.cpu_set);
                }
                Ok(())
            }
        }

        /// Remove a CPU from CpuSet.
        /// `field` is the CPU id to remove
        pub fn unset(&mut self, field: usize) -> Result<()> {
            if field >= CpuSet::count() {
                Err(Errno::EINVAL)
            } else {
                unsafe {
                    libc::CPU_CLR(field, &mut self.cpu_set);
                }
                Ok(())
            }
        }

        /// Return the maximum number of CPU in CpuSet
        pub const fn count() -> usize {
            #[cfg(not(target_os = "freebsd"))]
            let bytes = mem::size_of::<libc::cpu_set_t>();
            #[cfg(target_os = "freebsd")]
            let bytes = mem::size_of::<libc::cpuset_t>();

            8 * bytes
        }
    }

    impl Default for CpuSet {
        fn default() -> Self {
            Self::new()
        }
    }

    /// `sched_setaffinity` set a thread's CPU affinity mask
    /// ([`sched_setaffinity(2)`](https://man7.org/linux/man-pages/man2/sched_setaffinity.2.html))
    ///
    /// `pid` is the thread ID to update.
    /// If pid is zero, then the calling thread is updated.
    ///
    /// The `cpuset` argument specifies the set of CPUs on which the thread
    /// will be eligible to run.
    ///
    /// # Example
    ///
    /// Binding the current thread to CPU 0 can be done as follows:
    ///
    /// ```rust,no_run
    /// use nix::sched::{CpuSet, sched_setaffinity};
    /// use nix::unistd::Pid;
    ///
    /// let mut cpu_set = CpuSet::new();
    /// cpu_set.set(0).unwrap();
    /// sched_setaffinity(Pid::from_raw(0), &cpu_set).unwrap();
    /// ```
    pub fn sched_setaffinity(pid: Pid, cpuset: &CpuSet) -> Result<()> {
        let res = unsafe {
            libc::sched_setaffinity(
                pid.into(),
                mem::size_of::<CpuSet>() as libc::size_t,
                &cpuset.cpu_set,
            )
        };

        Errno::result(res).map(drop)
    }

    /// `sched_getaffinity` get a thread's CPU affinity mask
    /// ([`sched_getaffinity(2)`](https://man7.org/linux/man-pages/man2/sched_getaffinity.2.html))
    ///
    /// `pid` is the thread ID to check.
    /// If pid is zero, then the calling thread is checked.
    ///
    /// Returned `cpuset` is the set of CPUs on which the thread
    /// is eligible to run.
    ///
    /// # Example
    ///
    /// Checking if the current thread can run on CPU 0 can be done as follows:
    ///
    /// ```rust,no_run
    /// use nix::sched::sched_getaffinity;
    /// use nix::unistd::Pid;
    ///
    /// let cpu_set = sched_getaffinity(Pid::from_raw(0)).unwrap();
    /// if cpu_set.is_set(0).unwrap() {
    ///     println!("Current thread can run on CPU 0");
    /// }
    /// ```
    pub fn sched_getaffinity(pid: Pid) -> Result<CpuSet> {
        let mut cpuset = CpuSet::new();
        let res = unsafe {
            libc::sched_getaffinity(
                pid.into(),
                mem::size_of::<CpuSet>() as libc::size_t,
                &mut cpuset.cpu_set,
            )
        };

        Errno::result(res).and(Ok(cpuset))
    }

    /// Determines the CPU on which the calling thread is running.
    pub fn sched_getcpu() -> Result<usize> {
        let res = unsafe { libc::sched_getcpu() };

        Errno::result(res).map(|int| int as usize)
    }
}

/// Explicitly yield the processor to other threads.
///
/// [Further reading](https://pubs.opengroup.org/onlinepubs/9699919799/functions/sched_yield.html)
pub fn sched_yield() -> Result<()> {
    let res = unsafe { libc::sched_yield() };

    Errno::result(res).map(drop)
}