1 // SPDX-License-Identifier: GPL-2.0 2 3 //! Tasks (threads and processes). 4 //! 5 //! C header: [`include/linux/sched.h`](../../../../include/linux/sched.h). 6 7 use crate::{bindings, types::Opaque}; 8 use core::ptr; 9 10 /// Wraps the kernel's `struct task_struct`. 11 /// 12 /// # Invariants 13 /// 14 /// All instances are valid tasks created by the C portion of the kernel. 15 /// 16 /// Instances of this type are always ref-counted, that is, a call to `get_task_struct` ensures 17 /// that the allocation remains valid at least until the matching call to `put_task_struct`. 18 #[repr(transparent)] 19 pub struct Task(pub(crate) Opaque<bindings::task_struct>); 20 21 // SAFETY: It's OK to access `Task` through references from other threads because we're either 22 // accessing properties that don't change (e.g., `pid`, `group_leader`) or that are properly 23 // synchronised by C code (e.g., `signal_pending`). 24 unsafe impl Sync for Task {} 25 26 /// The type of process identifiers (PIDs). 27 type Pid = bindings::pid_t; 28 29 impl Task { 30 /// Returns the group leader of the given task. 31 pub fn group_leader(&self) -> &Task { 32 // SAFETY: By the type invariant, we know that `self.0` is a valid task. Valid tasks always 33 // have a valid group_leader. 34 let ptr = unsafe { *ptr::addr_of!((*self.0.get()).group_leader) }; 35 36 // SAFETY: The lifetime of the returned task reference is tied to the lifetime of `self`, 37 // and given that a task has a reference to its group leader, we know it must be valid for 38 // the lifetime of the returned task reference. 39 unsafe { &*ptr.cast() } 40 } 41 42 /// Returns the PID of the given task. 43 pub fn pid(&self) -> Pid { 44 // SAFETY: By the type invariant, we know that `self.0` is a valid task. Valid tasks always 45 // have a valid pid. 46 unsafe { *ptr::addr_of!((*self.0.get()).pid) } 47 } 48 49 /// Determines whether the given task has pending signals. 50 pub fn signal_pending(&self) -> bool { 51 // SAFETY: By the type invariant, we know that `self.0` is valid. 52 unsafe { bindings::signal_pending(self.0.get()) != 0 } 53 } 54 55 /// Wakes up the task. 56 pub fn wake_up(&self) { 57 // SAFETY: By the type invariant, we know that `self.0.get()` is non-null and valid. 58 // And `wake_up_process` is safe to be called for any valid task, even if the task is 59 // running. 60 unsafe { bindings::wake_up_process(self.0.get()) }; 61 } 62 } 63 64 // SAFETY: The type invariants guarantee that `Task` is always ref-counted. 65 unsafe impl crate::types::AlwaysRefCounted for Task { 66 fn inc_ref(&self) { 67 // SAFETY: The existence of a shared reference means that the refcount is nonzero. 68 unsafe { bindings::get_task_struct(self.0.get()) }; 69 } 70 71 unsafe fn dec_ref(obj: ptr::NonNull<Self>) { 72 // SAFETY: The safety requirements guarantee that the refcount is nonzero. 73 unsafe { bindings::put_task_struct(obj.cast().as_ptr()) } 74 } 75 } 76