runtime: optimize for speed and fix deadlock

The previous method of taking the channel could cause deadlock, we now
use semaphore to signal if the channel is available instead of busy
polling the mutex.

src/Cargo.lock

@@ -187,7 +187,7 @@ dependencies = [
 [[package]]
 name = "libasync"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#a73df780d0d0e757738f27feac162904f5bf93f9"
+source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#157439bc88cbb18bb40009428acf1fdee800e32e"
 dependencies = [
  "embedded-hal",
  "libcortex_a9",
@@ -199,7 +199,7 @@ dependencies = [
 [[package]]
 name = "libboard_zynq"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#a73df780d0d0e757738f27feac162904f5bf93f9"
+source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#157439bc88cbb18bb40009428acf1fdee800e32e"
 dependencies = [
  "bit_field",
  "embedded-hal",
@@ -233,7 +233,7 @@ dependencies = [
 [[package]]
 name = "libcortex_a9"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#a73df780d0d0e757738f27feac162904f5bf93f9"
+source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#157439bc88cbb18bb40009428acf1fdee800e32e"
 dependencies = [
  "bit_field",
  "libregister",
@@ -249,7 +249,7 @@ checksum = "c7d73b3f436185384286bd8098d17ec07c9a7d2388a6599f824d8502b529702a"
 [[package]]
 name = "libregister"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#a73df780d0d0e757738f27feac162904f5bf93f9"
+source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#157439bc88cbb18bb40009428acf1fdee800e32e"
 dependencies = [
  "bit_field",
  "vcell",
@@ -259,7 +259,7 @@ dependencies = [
 [[package]]
 name = "libsupport_zynq"
 version = "0.0.0"
-source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#a73df780d0d0e757738f27feac162904f5bf93f9"
+source = "git+https://git.m-labs.hk/M-Labs/zynq-rs.git#157439bc88cbb18bb40009428acf1fdee800e32e"
 dependencies = [
  "compiler_builtins",
  "libboard_zynq",

src/Cargo.toml

@@ -24,7 +24,7 @@ overflow-checks = false
 panic = "abort"
 debug = true
 codegen-units = 1
-opt-level = 's'
+opt-level = 2
 lto = true
 
 [patch.crates-io]

src/runtime/src/kernel/control.rs

@@ -1,7 +1,7 @@
 use libcortex_a9::sync_channel::{Sender, Receiver};
 use libsupport_zynq::boot::Core1;
 
-use super::{CHANNEL_0TO1, CHANNEL_1TO0, INIT_LOCK, Message};
+use super::{CHANNEL_0TO1, CHANNEL_1TO0, CHANNEL_SEM, INIT_LOCK, Message};
 use crate::irq::restart_core1;
 
 use core::mem::{forget, replace};
@@ -12,6 +12,7 @@ pub struct Control {
 }
 
 fn get_channels() -> (Sender<'static, Message>, Receiver<'static, Message>) {
+    CHANNEL_SEM.wait();
     let mut core0_tx = None;
     while core0_tx.is_none() {
         core0_tx = CHANNEL_0TO1.lock().take();

src/runtime/src/kernel/core1.rs

@@ -20,6 +20,7 @@ use super::{
     rpc::rpc_send_async,
     INIT_LOCK,
     CHANNEL_0TO1, CHANNEL_1TO0,
+    CHANNEL_SEM,
     KERNEL_CHANNEL_0TO1, KERNEL_CHANNEL_1TO0,
     KERNEL_IMAGE,
     Message,
@@ -159,6 +160,7 @@ pub fn main_core1() {
     }
     *CHANNEL_0TO1.lock() = Some(core0_tx);
     *CHANNEL_1TO0.lock() = Some(core0_rx);
+    CHANNEL_SEM.signal();
 
     // set on load, cleared on start
     let mut loaded_kernel = None;

src/runtime/src/kernel/mod.rs

@@ -1,7 +1,7 @@
 use core::ptr;
 use alloc::{vec::Vec, string::String};
 
-use libcortex_a9::{mutex::Mutex, sync_channel};
+use libcortex_a9::{mutex::Mutex, sync_channel, semaphore::Semaphore};
 use crate::eh_artiq;
 
 mod control;
@@ -48,6 +48,7 @@ pub enum Message {
 
 static CHANNEL_0TO1: Mutex<Option<sync_channel::Sender<'static, Message>>> = Mutex::new(None);
 static CHANNEL_1TO0: Mutex<Option<sync_channel::Receiver<'static, Message>>> = Mutex::new(None);
+static CHANNEL_SEM: Semaphore = Semaphore::new(0, 1);
 
 static mut KERNEL_CHANNEL_0TO1: Option<sync_channel::Receiver<'static, Message>> = None;
 static mut KERNEL_CHANNEL_1TO0: Option<sync_channel::Sender<'static, Message>> = None;