playwav: Yield cpu while waiting for audio to catch up

userspace/playwav/src/main.rs

@@ -33,6 +33,13 @@ fn play(song: &str) -> Result<(), ExitCode> {
     )
     .map_err(|_e| ExitCode::from(4))?;
 
+    for addr in (wav_map..wav_map + wav_size).step_by(4096) {
+        let _ = unsafe {
+            // prefault to read the file into memory
+            (addr as *const u64).read_volatile()
+        };
+    }
+
     //println!("file size: {}", wav_size);
 
     let get_current_hda_block =
@@ -52,7 +59,10 @@ fn play(song: &str) -> Result<(), ExitCode> {
 
         let chunk = std::cmp::min(rem, 2048);
 
-        while ((get_current_hda_block() + 3) % buf_block_count) != wp_block {}
+        while ((get_current_hda_block() + 3) % buf_block_count) != wp_block {
+            // yield cpu for other tasks
+            let _ = syscall_user::yield_execution();
+        }
 
         hda_data[wp_block * 2048..wp_block * 2048 + chunk]
             .copy_from_slice(&wav_data[file_block * 2048..file_block * 2048 + chunk]);
@@ -61,7 +71,10 @@ fn play(song: &str) -> Result<(), ExitCode> {
         file_block += 1;
     }
 
-    while get_current_hda_block() != wp_block {}
+    while get_current_hda_block() != wp_block {
+        // yield cpu for other tasks
+        let _ = syscall_user::yield_execution();
+    }
 
     hda_data.fill(0); //silence
 

userspace/shell/src/nc.rs

@@ -56,7 +56,7 @@ fn recv(fd: usize) -> bool {
 
 fn start(fd: usize) {
     unsafe {
-        SENT = 0;
+        (&raw mut SENT).write(0);
     }
 
     let mut read_fds: FdSet = FdSet::new();

userspace/syscall-user/src/lib.rs

@@ -482,6 +482,10 @@ pub fn ioctl(fd: usize, cmd: usize, arg: usize) -> SyscallResult {
     unsafe { syscall3(SYS_IOCTL, fd, cmd, arg) }
 }
 
+pub fn yield_execution() -> SyscallResult {
+    unsafe { syscall0(SYS_YIELD) }
+}
+
 pub fn sigaction(
     sig: usize,
     mut sigaction: Option<&mut syscall_defs::signal::SigAction>,