WIP: Fix userspace ACPI shutdown.

src/arch/x86_64/stop.rs

@@ -27,29 +27,47 @@ pub unsafe extern fn kreset() -> ! {
     unreachable!();
 }
 
-#[no_mangle]
-pub unsafe extern fn kstop() -> ! {
-    println!("kstop");
+#[cfg(feature = "acpi")]
+fn userspace_acpi_shutdown() {
+    log::info!("Notifying any potential ACPI driver");
+    // Tell whatever driver that handles ACPI, that it should enter the S5 state (i.e.
+    // shutdown).
+    if ! acpi::register_kstop() {
+        // There was no context to switch to.
+        log::info!("No ACPI driver was alive to handle shutdown.");
+        return;
+    }
+    log::info!("Waiting one second for ACPI driver to run the shutdown sequence.");
+    let (initial_s, initial_ns) = time::monotonic();
 
-    // FIXME: RPC into userspace, maybe allowing the kernel ACPI scheme to support e.g. registering
-    // an event queue, so that a special file can only be read/written when about to shut down.
+    // Since this driver is a userspace process, and we do not use any magic like directly
+    // context switching, we have to wait for the userspace driver to complete, with a timeout.
+    //
+    // We switch context, and wait for one second.
+    loop {
+        // TODO: Switch directly to whichever process is handling the kstop pipe. We would add an
+        // event flag like EVENT_DIRECT, which has already been suggested for IRQs.
+        // TODO: Waitpid with timeout? Because, what if the ACPI driver would crash?
+        let _ = unsafe { context::switch() };
+        let (current_s, current_ns) = time::monotonic();
 
-    #[cfg(feature = "acpi")]
-    {
-        // Tell whatever driver that handles ACPI, that it should enter the S5 state (i.e.
-        // shutdown).
-        acpi::register_kstop();
+        let diff_s = current_s - initial_s;
+        let diff_part_ns = current_ns - initial_ns;
+        let diff_ns = diff_s * 1_000_000_000 + diff_part_ns;
 
-        // Since this driver is a userspace process, and we do not use any magic like directly
-        // context switching, we have to wait for the userspace driver to complete, with a timeout.
-        //
-        // We switch context, and wait for one second.
-        while time::monotonic().0 < 1 {
-            if ! context::switch() {
-                break;
-            }
+        if diff_ns > 1_000_000_000 {
+            log::info!("Timeout reached, thus falling back to other shutdown methods.");
+            return;
         }
     }
+}
+
+#[no_mangle]
+pub unsafe extern fn kstop() -> ! {
+    log::info!("Running kstop()");
+
+    #[cfg(feature = "acpi")]
+    userspace_acpi_shutdown();
 
     // Magic shutdown code for bochs and qemu (older versions).
     for c in "Shutdown".bytes() {

src/context/context.rs

@@ -34,7 +34,7 @@ pub enum Status {
     Runnable,
     Blocked,
     Stopped(usize),
-    Exited(usize)
+    Exited(usize),
 }
 
 #[derive(Copy, Clone, Debug)]

src/syscall/process.rs

@@ -1128,6 +1128,8 @@ pub fn fexec(fd: FileHandle, arg_ptrs: &[[usize; 2]], var_ptrs: &[[usize; 2]]) -
 pub fn exit(status: usize) -> ! {
     ptrace::breakpoint_callback(PTRACE_STOP_EXIT, Some(ptrace_event!(PTRACE_STOP_EXIT, status)));
 
+    let pid;
+
     {
         let context_lock = {
             let contexts = context::contexts();
@@ -1136,7 +1138,7 @@ pub fn exit(status: usize) -> ! {
         };
 
         let mut close_files = Vec::new();
-        let pid = {
+        pid = {
             let mut context = context_lock.write();
             {
                 let mut lock = context.files.write();
@@ -1148,6 +1150,22 @@ pub fn exit(status: usize) -> ! {
             context.id
         };
 
+        // TODO: Find a better way to implement this, perhaps when the init process calls exit.
+        if pid == ContextId::from(1) {
+            println!("Main kernel thread exited with status {:X}", status);
+
+            extern {
+                fn kreset() -> !;
+                fn kstop() -> !;
+            }
+
+            if status == SIGTERM {
+                unsafe { kreset(); }
+            } else {
+                unsafe { kstop(); }
+            }
+        }
+
         // Files must be closed while context is valid so that messages can be passed
         for (_fd, file_opt) in close_files.drain(..).enumerate() {
             if let Some(file) = file_opt {
@@ -1214,26 +1232,10 @@ pub fn exit(status: usize) -> ! {
 
         // Alert any tracers waiting of this process
         ptrace::close_tracee(pid);
-
-        if pid == ContextId::from(1) {
-            println!("Main kernel thread exited with status {:X}", status);
-
-            extern {
-                fn kreset() -> !;
-                fn kstop() -> !;
-            }
-
-            if status == SIGTERM {
-                unsafe { kreset(); }
-            } else {
-                unsafe { kstop(); }
-            }
-        }
     }
 
     let _ = unsafe { context::switch() };
-
-    unreachable!();
+    unreachable!()
 }
 
 pub fn getpid() -> Result<ContextId> {