firmware: workaround for RPC failures

artiq/firmware/ksupport/lib.rs

@@ -101,6 +101,7 @@ mod api;
 mod rtio;
 mod nrt_bus;
 
+static mut NOW: u64 = 0;
 static mut LIBRARY: Option<Library<'static>> = None;
 
 #[no_mangle]
@@ -185,6 +186,7 @@ fn terminate(exception: &eh_artiq::Exception, backtrace: &mut [usize]) -> ! {
     }
     let backtrace = &mut backtrace.as_mut()[0..cursor];
 
+    send(&NowSave(unsafe { NOW }));
     send(&RunException {
         exception: kernel_proto::Exception {
             name:     str::from_utf8(exception.name.as_ref()).unwrap(),
@@ -508,7 +510,10 @@ pub unsafe fn main() {
 
     ptr::write_bytes(__bss_start as *mut u8, 0, (_end - __bss_start) as usize);
 
+    send(&NowInitRequest);
+    recv!(&NowInitReply(now) => NOW = now);
     (mem::transmute::<u32, fn()>(__modinit__))();
+    send(&NowSave(NOW));
 
     if let Some(typeinfo) = typeinfo {
         attribute_writeback(typeinfo as *const ());

artiq/firmware/libproto_artiq/kernel_proto.rs

@@ -22,6 +22,10 @@ pub enum Message<'a> {
     LoadRequest(&'a [u8]),
     LoadReply(Result<(), dyld::Error<'a>>),
 
+    NowInitRequest,
+    NowInitReply(u64),
+    NowSave(u64),
+
     RtioInitRequest,
 
     RtioDestinationStatusRequest { destination: u8 },

artiq/firmware/runtime/session.rs

@@ -63,6 +63,7 @@ macro_rules! unexpected {
 // Persistent state
 #[derive(Debug)]
 struct Congress {
+    now: u64,
     cache: Cache,
     dma_manager: DmaManager,
     finished_cleanly: Cell<bool>
@@ -71,6 +72,7 @@ struct Congress {
 impl Congress {
     fn new() -> Congress {
         Congress {
+            now: 0,
             cache: Cache::new(),
             dma_manager: DmaManager::new(),
             finished_cleanly: Cell::new(true)
@@ -363,6 +365,14 @@ fn process_kern_message(io: &Io, aux_mutex: &Mutex,
                 kern_acknowledge()
             }
 
+            &kern::NowInitRequest =>
+                kern_send(io, &kern::NowInitReply(session.congress.now)),
+
+            &kern::NowSave(now) => {
+                session.congress.now = now;
+                kern_acknowledge()
+            }
+
             &kern::DmaRecordStart(name) => {
                 session.congress.dma_manager.record_start(name);
                 kern_acknowledge()