defmt-rtt: Update to critical-section 1.0

Author: Dirbaio

firmware/defmt-rtt/Cargo.toml

@@ -12,4 +12,4 @@ version = "0.3.2"
 
 [dependencies]
 defmt = { version = "0.3", path = "../../defmt" }
-critical-section = "0.2.5"
+critical-section = "1.0.0-alpha.2"

firmware/defmt-rtt/src/lib.rs

@@ -22,7 +22,7 @@
 
 mod channel;
 
-use core::sync::atomic::{AtomicBool, AtomicU8, AtomicUsize, Ordering};
+use core::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 
 use crate::channel::Channel;
 
@@ -37,13 +37,13 @@ struct Logger;
 
 /// Global logger lock.
 static TAKEN: AtomicBool = AtomicBool::new(false);
-static INTERRUPTS_ACTIVE: AtomicU8 = AtomicU8::new(0);
+static mut CS_RESTORE: critical_section::RestoreState = critical_section::RestoreState::invalid();
 static mut ENCODER: defmt::Encoder = defmt::Encoder::new();
 
 unsafe impl defmt::Logger for Logger {
     fn acquire() {
         // safety: Must be paired with corresponding call to release(), see below
-        let token = unsafe { critical_section::acquire() };
+        let restore = unsafe { critical_section::acquire() };
 
         if TAKEN.load(Ordering::Relaxed) {
             panic!("defmt logger taken reentrantly")
@@ -52,9 +52,10 @@ unsafe impl defmt::Logger for Logger {
         // no need for CAS because interrupts are disabled
         TAKEN.store(true, Ordering::Relaxed);
 
-        INTERRUPTS_ACTIVE.store(token, Ordering::Relaxed);
+        // safety: accessing the `static mut` is OK because we have acquired a critical section.
+        unsafe { CS_RESTORE = restore };
 
-        // safety: accessing the `static mut` is OK because we have disabled interrupts.
+        // safety: accessing the `static mut` is OK because we have acquired a critical section.
         unsafe { ENCODER.start_frame(do_write) }
     }
 
@@ -64,16 +65,20 @@ unsafe impl defmt::Logger for Logger {
     }
 
     unsafe fn release() {
-        // safety: accessing the `static mut` is OK because we have disabled interrupts.
+        // safety: accessing the `static mut` is OK because we have acquired a critical section.
         ENCODER.end_frame(do_write);
 
         TAKEN.store(false, Ordering::Relaxed);
+
+        // safety: accessing the `static mut` is OK because we have acquired a critical section.
+        let restore = CS_RESTORE;
+
         // safety: Must be paired with corresponding call to acquire(), see above
-        critical_section::release(INTERRUPTS_ACTIVE.load(Ordering::Relaxed));
+        critical_section::release(restore);
     }
 
     unsafe fn write(bytes: &[u8]) {
-        // safety: accessing the `static mut` is OK because we have disabled interrupts.
+        // safety: accessing the `static mut` is OK because we have acquired a critical section.
         ENCODER.write(bytes, do_write);
     }
 }