esp-println: avoid double locking when using auto

esp-println/src/defmt.rs

@@ -4,7 +4,7 @@
 #[cfg(feature = "critical-section")]
 use critical_section::RestoreState;
 
-use super::PrinterImpl;
+use super::{LockToken, PrinterImpl};
 
 /// Global logger lock.
 #[cfg(feature = "critical-section")]
@@ -74,7 +74,12 @@ unsafe impl defmt::Logger for Logger {
     }
 
     unsafe fn flush() {
-        PrinterImpl::flush();
+        let token = unsafe {
+            // Safety: the implementation ensures this is only called in a critical
+            // section.
+            LockToken::conjure()
+        };
+        PrinterImpl::flush(token);
     }
 
     unsafe fn write(bytes: &[u8]) {
@@ -85,5 +90,10 @@ unsafe impl defmt::Logger for Logger {
 }
 
 fn do_write(bytes: &[u8]) {
-    PrinterImpl::write_bytes_assume_cs(bytes)
+    let token = unsafe {
+        // Safety: the above implementation ensures this is only called in a critical
+        // section.
+        LockToken::conjure()
+    };
+    PrinterImpl::write_bytes_in_cs(bytes, token)
 }

esp-println/src/lib.rs

@@ -87,9 +87,9 @@ impl core::fmt::Write for Printer {
 impl Printer {
     /// Writes a byte slice to the configured output.
     pub fn write_bytes(bytes: &[u8]) {
-        with(|| {
-            PrinterImpl::write_bytes_assume_cs(bytes);
-            PrinterImpl::flush();
+        with(|token| {
+            PrinterImpl::write_bytes_in_cs(bytes, token);
+            PrinterImpl::flush(token);
         })
     }
 }
@@ -114,10 +114,10 @@ type PrinterImpl = auto_printer::Printer;
     )
 ))]
 mod auto_printer {
-    use super::with;
     use crate::{
         serial_jtag_printer::Printer as PrinterSerialJtag,
         uart_printer::Printer as PrinterUart,
+        LockToken,
     };
 
     pub struct Printer;
@@ -145,27 +145,19 @@ mod auto_printer {
             unsafe { (USB_DEVICE_INT_RAW.read_volatile() & SOF_INT_MASK) != 0 }
         }
 
-        pub fn write_bytes_assume_cs(bytes: &[u8]) {
+        pub fn write_bytes_in_cs(bytes: &[u8], token: LockToken<'_>) {
             if Self::use_jtag() {
-                with(|| {
-                    PrinterSerialJtag::write_bytes_assume_cs(bytes);
-                })
+                PrinterSerialJtag::write_bytes_in_cs(bytes, token);
             } else {
-                with(|| {
-                    PrinterUart::write_bytes_assume_cs(bytes);
-                })
+                PrinterUart::write_bytes_in_cs(bytes, token);
             }
         }
 
-        pub fn flush() {
+        pub fn flush(token: LockToken<'_>) {
             if Self::use_jtag() {
-                with(|| {
-                    PrinterSerialJtag::flush();
-                })
+                PrinterSerialJtag::flush(token);
             } else {
-                with(|| {
-                    PrinterUart::flush();
-                })
+                PrinterUart::flush(token);
             }
         }
     }
@@ -198,6 +190,8 @@ mod auto_printer {
 ))]
 mod serial_jtag_printer {
     use portable_atomic::{AtomicBool, Ordering};
+
+    use super::LockToken;
     pub struct Printer;
 
     #[cfg(feature = "esp32c3")]
@@ -256,7 +250,7 @@ mod serial_jtag_printer {
     }
 
     impl Printer {
-        pub fn write_bytes_assume_cs(bytes: &[u8]) {
+        pub fn write_bytes_in_cs(bytes: &[u8], _token: LockToken<'_>) {
             if fifo_full() {
                 // The FIFO is full. Let's see if we can progress.
 
@@ -289,19 +283,20 @@ mod serial_jtag_printer {
             }
         }
 
-        pub fn flush() {
+        pub fn flush(_token: LockToken<'_>) {
             fifo_flush();
         }
     }
 }
 
 #[cfg(all(any(feature = "uart", feature = "auto"), feature = "esp32"))]
 mod uart_printer {
+    use super::LockToken;
     const UART_TX_ONE_CHAR: usize = 0x4000_9200;
 
     pub struct Printer;
     impl Printer {
-        pub fn write_bytes_assume_cs(bytes: &[u8]) {
+        pub fn write_bytes_in_cs(bytes: &[u8], _token: LockToken<'_>) {
             for &b in bytes {
                 unsafe {
                     let uart_tx_one_char: unsafe extern "C" fn(u8) -> i32 =
@@ -311,15 +306,16 @@ mod uart_printer {
             }
         }
 
-        pub fn flush() {}
+        pub fn flush(_token: LockToken<'_>) {}
     }
 }
 
 #[cfg(all(any(feature = "uart", feature = "auto"), feature = "esp32s2"))]
 mod uart_printer {
+    use super::LockToken;
     pub struct Printer;
     impl Printer {
-        pub fn write_bytes_assume_cs(bytes: &[u8]) {
+        pub fn write_bytes_in_cs(bytes: &[u8], _token: LockToken<'_>) {
             // On ESP32-S2 the UART_TX_ONE_CHAR ROM-function seems to have some issues.
             for chunk in bytes.chunks(64) {
                 for &b in chunk {
@@ -338,7 +334,7 @@ mod uart_printer {
             }
         }
 
-        pub fn flush() {}
+        pub fn flush(_token: LockToken<'_>) {}
     }
 }
 
@@ -347,6 +343,7 @@ mod uart_printer {
     not(any(feature = "esp32", feature = "esp32s2"))
 ))]
 mod uart_printer {
+    use super::LockToken;
     trait Functions {
         const TX_ONE_CHAR: usize;
         const CHUNK_SIZE: usize = 32;
@@ -459,7 +456,7 @@ mod uart_printer {
 
     pub struct Printer;
     impl Printer {
-        pub fn write_bytes_assume_cs(bytes: &[u8]) {
+        pub fn write_bytes_in_cs(bytes: &[u8], _token: LockToken<'_>) {
             for chunk in bytes.chunks(Device::CHUNK_SIZE) {
                 for &b in chunk {
                     Device::tx_byte(b);
@@ -469,15 +466,36 @@ mod uart_printer {
             }
         }
 
-        pub fn flush() {}
+        pub fn flush(_token: LockToken<'_>) {}
+    }
+}
+
+#[cfg(not(feature = "critical-section"))]
+type LockInner<'a> = PhantomData<&'a ()>;
+#[cfg(feature = "critical-section")]
+type LockInner<'a> = critical_section::CriticalSection<'a>;
+
+#[derive(Clone, Copy)]
+struct LockToken<'a>(LockInner<'a>);
+
+impl<'a> LockToken<'a> {
+    #[allow(unused)]
+    unsafe fn conjure() -> Self {
+        #[cfg(feature = "critical-section")]
+        let inner = critical_section::CriticalSection::new();
+        #[cfg(not(feature = "critical-section"))]
+        let inner = PhantomData;
+
+        LockToken(inner)
     }
 }
 
+/// Runs the callback in a critical section, if enabled.
 #[inline]
-fn with<R>(f: impl FnOnce() -> R) -> R {
+fn with<R>(f: impl FnOnce(LockToken) -> R) -> R {
     #[cfg(feature = "critical-section")]
-    return critical_section::with(|_| f());
+    return critical_section::with(|cs| f(LockToken(cs)));
 
     #[cfg(not(feature = "critical-section"))]
-    f()
+    f(unsafe { LockToken::conjure() })
 }