Kernel: Add try_print! and try_println!

moon/src/log.rs

@@ -1,19 +1,48 @@
 use crate::arch::io::SERIAL;
 use core::fmt;
 
+/// Locks the serial port and writes formatted output.
 #[macro_export]
 macro_rules! print {
     ($($arg:tt)*) => ($crate::log::_print(format_args!($($arg)*)));
 }
 
+/// Tries to lock the serial port and writes formatted output.
+/// Should be used in interrupt handlers, as it does not block but silently fails. 
+/// (If we are blocked waiting for interrupted code to unlock a lock, that's an instant deadlock unless we are on SMP and another CPU schedules that code)
+#[macro_export]
+macro_rules! try_print {
+    ($($arg:tt)*) => ($crate::log::_try_print(format_args!($($arg)*)));
+}
+
+/// Locks the serial port and writes formatted output with a trailing newline.
 #[macro_export]
 macro_rules! println {
     () => ($crate::print!("\n"));
     ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
 }
 
+/// Tries to lock the serial port and writes formatted output with a trailing newline.
+/// Should be used in interrupt handlers, as it does not block but silently fails. 
+/// (If we are blocked waiting for interrupted code to unlock a lock, that's an instant deadlock unless we are on SMP and another CPU schedules that code)
+#[macro_export]
+macro_rules! try_println {
+    () => ($crate::try_print!("\n"));
+    ($($arg:tt)*) => ($crate::try_print!("{}\n", format_args!($($arg)*)));
+}
+
 #[doc(hidden)]
 pub fn _print(args: fmt::Arguments) {
     use core::fmt::Write;
     SERIAL.lock().write_fmt(args).unwrap();
 }
+
+#[doc(hidden)]
+pub fn _try_print(args: fmt::Arguments) {
+    use core::fmt::Write;
+    let serial = SERIAL.try_lock();
+    if serial.is_some()
+    {
+        serial.unwrap().write_fmt(args).unwrap();
+    }
+}