diff options
Diffstat (limited to 'library/std/src/sys/itron/thread.rs')
-rw-r--r-- | library/std/src/sys/itron/thread.rs | 48 |
1 files changed, 30 insertions, 18 deletions
diff --git a/library/std/src/sys/itron/thread.rs b/library/std/src/sys/itron/thread.rs index d28f57f33..c2b366808 100644 --- a/library/std/src/sys/itron/thread.rs +++ b/library/std/src/sys/itron/thread.rs @@ -11,18 +11,25 @@ use crate::{ ffi::CStr, hint, io, mem::ManuallyDrop, + ptr::NonNull, sync::atomic::{AtomicUsize, Ordering}, sys::thread_local_dtor::run_dtors, time::Duration, }; pub struct Thread { - inner: ManuallyDrop<Box<ThreadInner>>, + p_inner: NonNull<ThreadInner>, /// The ID of the underlying task. task: abi::ID, } +// Safety: There's nothing in `Thread` that ties it to the original creator. It +// can be dropped by any threads. +unsafe impl Send for Thread {} +// Safety: `Thread` provides no methods that take `&self`. +unsafe impl Sync for Thread {} + /// State data shared between a parent thread and child thread. It's dropped on /// a transition to one of the final states. struct ThreadInner { @@ -90,8 +97,9 @@ impl Thread { }); unsafe extern "C" fn trampoline(exinf: isize) { + let p_inner: *mut ThreadInner = crate::ptr::from_exposed_addr_mut(exinf as usize); // Safety: `ThreadInner` is alive at this point - let inner = unsafe { &*(exinf as *const ThreadInner) }; + let inner = unsafe { &*p_inner }; // Safety: Since `trampoline` is called only once for each // `ThreadInner` and only `trampoline` touches `start`, @@ -119,13 +127,13 @@ impl Thread { // No one will ever join, so we'll ask the collector task to // delete the task. - // In this case, `inner`'s ownership has been moved to us, - // And we are responsible for dropping it. The acquire + // In this case, `*p_inner`'s ownership has been moved to + // us, and we are responsible for dropping it. The acquire // ordering is not necessary because the parent thread made // no memory access needing synchronization since the call // to `acre_tsk`. // Safety: See above. - let _ = unsafe { Box::from_raw(inner as *const _ as *mut ThreadInner) }; + let _ = unsafe { Box::from_raw(p_inner) }; // Safety: There are no pinned references to the stack unsafe { terminate_and_delete_current_task() }; @@ -162,13 +170,14 @@ impl Thread { } } - let inner_ptr = (&*inner) as *const ThreadInner; + // Safety: `Box::into_raw` returns a non-null pointer + let p_inner = unsafe { NonNull::new_unchecked(Box::into_raw(inner)) }; let new_task = ItronError::err_if_negative(unsafe { abi::acre_tsk(&abi::T_CTSK { // Activate this task immediately tskatr: abi::TA_ACT, - exinf: inner_ptr as abi::EXINF, + exinf: p_inner.as_ptr().expose_addr() as abi::EXINF, // The entry point task: Some(trampoline), // Inherit the calling task's base priority @@ -180,7 +189,7 @@ impl Thread { }) .map_err(|e| e.as_io_error())?; - Ok(Self { inner: ManuallyDrop::new(inner), task: new_task }) + Ok(Self { p_inner, task: new_task }) } pub fn yield_now() { @@ -197,8 +206,9 @@ impl Thread { } } - pub fn join(mut self) { - let inner = &*self.inner; + pub fn join(self) { + // Safety: `ThreadInner` is alive at this point + let inner = unsafe { self.p_inner.as_ref() }; // Get the current task ID. Panicking here would cause a resource leak, // so just abort on failure. let current_task = task::current_task_id_aborting(); @@ -243,8 +253,8 @@ impl Thread { unsafe { terminate_and_delete_task(self.task) }; // In either case, we are responsible for dropping `inner`. - // Safety: The contents of `self.inner` will not be accessed hereafter - let _inner = unsafe { ManuallyDrop::take(&mut self.inner) }; + // Safety: The contents of `*p_inner` will not be accessed hereafter + let _inner = unsafe { Box::from_raw(self.p_inner.as_ptr()) }; // Skip the destructor (because it would attempt to detach the thread) crate::mem::forget(self); @@ -253,13 +263,16 @@ impl Thread { impl Drop for Thread { fn drop(&mut self) { + // Safety: `ThreadInner` is alive at this point + let inner = unsafe { self.p_inner.as_ref() }; + // Detach the thread. - match self.inner.lifecycle.swap(LIFECYCLE_DETACHED_OR_JOINED, Ordering::Acquire) { + match inner.lifecycle.swap(LIFECYCLE_DETACHED_OR_JOINED, Ordering::Acquire) { LIFECYCLE_INIT => { // [INIT → DETACHED] // When the time comes, the child will figure out that no // one will ever join it. - // The ownership of `self.inner` is moved to the child thread. + // The ownership of `*p_inner` is moved to the child thread. // However, the release ordering is not necessary because we // made no memory access needing synchronization since the call // to `acre_tsk`. @@ -278,10 +291,9 @@ impl Drop for Thread { // delete by entering the `FINISHED` state. unsafe { terminate_and_delete_task(self.task) }; - // Wwe are responsible for dropping `inner`. - // Safety: The contents of `self.inner` will not be accessed - // hereafter - unsafe { ManuallyDrop::drop(&mut self.inner) }; + // Wwe are responsible for dropping `*p_inner`. + // Safety: The contents of `*p_inner` will not be accessed hereafter + let _ = unsafe { Box::from_raw(self.p_inner.as_ptr()) }; } _ => unsafe { hint::unreachable_unchecked() }, } |