std: move locks to `sys` on µITRON

1 files changed, 68 insertions, 0 deletions

diff --git a/library/std/src/sys/locks/mutex/itron.rs b/library/std/src/sys/locks/mutex/itron.rs
new file mode 100644
index 00000000000..a134eb2d1be
--- /dev/null
+++ b/library/std/src/sys/locks/mutex/itron.rs
@@ -0,0 +1,68 @@
+//! Mutex implementation backed by μITRON mutexes. Assumes `acre_mtx` and
+//! `TA_INHERIT` are available.
+use crate::sys::pal::itron::{
+    abi,
+    error::{expect_success, expect_success_aborting, fail, ItronError},
+    spin::SpinIdOnceCell,
+};
+
+pub struct Mutex {
+    /// The ID of the underlying mutex object
+    mtx: SpinIdOnceCell<()>,
+}
+
+/// Create a mutex object. This function never panics.
+fn new_mtx() -> Result<abi::ID, ItronError> {
+    ItronError::err_if_negative(unsafe {
+        abi::acre_mtx(&abi::T_CMTX {
+            // Priority inheritance mutex
+            mtxatr: abi::TA_INHERIT,
+            // Unused
+            ceilpri: 0,
+        })
+    })
+}
+
+impl Mutex {
+    #[inline]
+    pub const fn new() -> Mutex {
+        Mutex { mtx: SpinIdOnceCell::new() }
+    }
+
+    /// Get the inner mutex's ID, which is lazily created.
+    fn raw(&self) -> abi::ID {
+        match self.mtx.get_or_try_init(|| new_mtx().map(|id| (id, ()))) {
+            Ok((id, ())) => id,
+            Err(e) => fail(e, &"acre_mtx"),
+        }
+    }
+
+    pub fn lock(&self) {
+        let mtx = self.raw();
+        expect_success(unsafe { abi::loc_mtx(mtx) }, &"loc_mtx");
+    }
+
+    pub unsafe fn unlock(&self) {
+        let mtx = unsafe { self.mtx.get_unchecked().0 };
+        expect_success_aborting(unsafe { abi::unl_mtx(mtx) }, &"unl_mtx");
+    }
+
+    pub fn try_lock(&self) -> bool {
+        let mtx = self.raw();
+        match unsafe { abi::ploc_mtx(mtx) } {
+            abi::E_TMOUT => false,
+            er => {
+                expect_success(er, &"ploc_mtx");
+                true
+            }
+        }
+    }
+}
+
+impl Drop for Mutex {
+    fn drop(&mut self) {
+        if let Some(mtx) = self.mtx.get().map(|x| x.0) {
+            expect_success_aborting(unsafe { abi::del_mtx(mtx) }, &"del_mtx");
+        }
+    }
+}