commit f615d73d776eb27e90baa6333a5462dcdc7d3934
author Andrew Walbran <qwandor@google.com> Mon Jul 22 14:41:09 2024 +0100
committer Andrew Walbran <qwandor@google.com> Tue Jul 23 16:24:52 2024 +0100
tree dd4e1d1c64421dd1cea4835fd16c2a4b2c4bf3ee
parent 5269681485f59673810d28e80f665131e519bbc3

Use Once<SpinMutex<Uart>> rather than SpinMutex<Option<Uart>> for consoles.

Test: m pvmfw
Change-Id: I61b514c568d78cd7050a264a2d6eae52b2814ba1

libs/libvmbase/src/console.rs

diff --git a/libs/libvmbase/src/console.rs b/libs/libvmbase/src/console.rs
index cd05250..7b01bb6 100644
--- a/libs/libvmbase/src/console.rs
+++ b/libs/libvmbase/src/console.rs
@@ -23,8 +23,8 @@
 // Matches the UART count in crosvm.
 const MAX_CONSOLES: usize = 4;
 
-static CONSOLES: [SpinMutex<Option<Uart>>; MAX_CONSOLES] =
-    [SpinMutex::new(None), SpinMutex::new(None), SpinMutex::new(None), SpinMutex::new(None)];
+static CONSOLES: [Once<SpinMutex<Uart>>; MAX_CONSOLES] =
+    [Once::new(), Once::new(), Once::new(), Once::new()];
 static ADDRESSES: [Once<usize>; MAX_CONSOLES] =
     [Once::new(), Once::new(), Once::new(), Once::new()];
 
@@ -48,10 +48,10 @@
         ADDRESSES[i].call_once(|| base_address);
 
         // Initialize the console driver, for normal console accesses.
-        let mut console = CONSOLES[i].lock();
-        assert!(console.is_none(), "console::init() called more than once");
-        // SAFETY: base_address must be the base of a mapped UART.
-        console.replace(unsafe { Uart::new(base_address) });
+        assert!(!CONSOLES[i].is_completed(), "console::init() called more than once");
+        // SAFETY: The caller promised that base_address is the base of a mapped UART with no
+        // aliases.
+        CONSOLES[i].call_once(|| SpinMutex::new(unsafe { Uart::new(base_address) }));
     }
 }
 
@@ -59,8 +59,7 @@
 ///
 /// Panics if the n-th console was not initialized by calling [`init`] first.
 pub fn writeln(n: usize, format_args: Arguments) {
-    let mut guard = CONSOLES[n].lock();
-    let uart = guard.as_mut().unwrap();
+    let uart = &mut *CONSOLES[n].get().unwrap().lock();
 
     write(uart, format_args).unwrap();
     let _ = uart.write_str("\n");