First chunk of work on a new scheduler

Author: farcaller

src/hal/systick.rs

@@ -0,0 +1,26 @@
+// Zinc, the bare metal stack for rust.
+// Copyright 2014 Vladimir "farcaller" Pouzanov <[email protected]>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/*!
+Interface to Systick timer.
+
+This might be merged into generic timer interface. Systick is a bit specific in
+terms of interrupts, but PT should make the difference negligible.
+*/
+
+pub trait Systick {
+  /// Starts the systick timer.
+  fn start(&self);
+}

src/os/sched/mod.rs

@@ -0,0 +1,20 @@
+// Zinc, the bare metal stack for rust.
+// Copyright 2014 Vladimir "farcaller" Pouzanov <[email protected]>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// Tasks scheduling and management.
+
+pub mod scheduler;
+pub mod stack;
+pub mod task;

src/os/sched/scheduler.rs

@@ -0,0 +1,206 @@
+// Zinc, the bare metal stack for rust.
+// Copyright 2014 Vladimir "farcaller" Pouzanov <[email protected]>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/*!
+Basic round-robin scheduler.
+
+TODO(farcaller): it's not round-robin, actually. A stricter time slice
+                 accounting must be done.
+*/
+
+use core::collections::Collection;
+
+use super::task;
+use super::stack::StackManager;
+use hal::systick::Systick;
+
+/// Scheduler interface.
+pub struct Scheduler<'a, T, S> {
+  index: task::TasksIndex<'a>,
+  context_switch: ||:'a,
+  systick: &'a T,
+  stack_manager: &'a S,
+}
+
+impl<'a, T: Systick, S: StackManager> Scheduler<'a, T, S> {
+  /// Creates a new scheduler given a list of tasks, systick timer and
+  /// management routines.
+  ///
+  /// At least one task must be defined in task index.
+  pub fn new(ti: task::TasksIndex<'a>, systick: &'a T,
+      stack_manager: &'a S, ctx_switch: ||:'a)
+    -> Scheduler<'a, T, S> {
+    Scheduler {
+      index: ti,
+      context_switch: ctx_switch,
+      systick: systick,
+      stack_manager: stack_manager,
+    }
+  }
+
+  /// Starts a scheduler and switches to first task. Never returns.
+  pub fn start(&mut self) {
+    self.stack_manager.set_task_stack_pointer(self.index.tasks[0].stack_start);
+    self.systick.start();
+    (self.context_switch)();
+  }
+
+  /// Switches to next task.
+  ///
+  /// Intended to be run by systick ISR, not invoked directly.
+  pub fn switch(&mut self) {
+    self.index.tasks[self.index.current_task_index as uint].stack_start =
+        self.stack_manager.get_task_stack_pointer();
+
+    self.index.current_task_index += 1;
+    if (self.index.current_task_index as uint) == self.index.tasks.len() {
+      self.index.current_task_index = 0;
+    }
+
+    self.stack_manager.set_task_stack_pointer(
+        self.index.tasks[self.index.current_task_index as uint].stack_start);
+  }
+
+  fn current_task_index(&self) -> u8 {
+    self.index.current_task_index
+  }
+
+  fn index(&self) -> &task::TasksIndex {
+    &self.index
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use hamcrest::{assert_that, is, equal_to};
+  use std::cell::Cell;
+  use std::kinds::marker;
+
+  use hal::systick::Systick;
+  use os::sched::stack::StackManager;
+  use os::sched::task;
+  use super::Scheduler;
+
+  struct FakeSystick {
+    pub started: Cell<bool>
+  }
+
+  impl FakeSystick {
+    pub fn new() -> FakeSystick { FakeSystick { started: Cell::new(false) } }
+  }
+  impl Systick for FakeSystick {
+    fn start(&self) { self.started.set(true); }
+  }
+
+  struct FakeStackManager {
+    pub sp: Cell<u32>
+  }
+  impl FakeStackManager {
+    pub fn new() -> FakeStackManager { FakeStackManager { sp: Cell::new(0) } }
+  }
+  impl StackManager for FakeStackManager {
+    fn get_task_stack_pointer(&self) -> u32 {
+      self.sp.get()
+    }
+    fn set_task_stack_pointer(&self, sp: u32) {
+      self.sp.set(sp);
+    }
+  }
+
+  describe!(
+    before_each {
+      let tick = FakeSystick::new();
+      let mut tasks = [task::Task {
+        state: task::Runnable,
+        stack_start: 100,
+        stack_end: 200,
+      },
+      task::Task {
+        state: task::Runnable,
+        stack_start: 200,
+        stack_end: 300,
+      }];
+      let ti = task::TasksIndex {
+        tasks: tasks,
+        current_task_index: 0,
+        no_copy: marker::NoCopy,
+      };
+      let fsm = FakeStackManager::new();
+    }
+
+    it "calls a context switch with first task" {
+      let mut called = false;
+
+      {
+        let mut scheduler = Scheduler::new(ti, &tick, &fsm, || { called = true });
+        scheduler.start();
+      }
+
+      assert_that(called, is(equal_to(true)));
+    }
+
+    it "schedules second task on timer interrupt" {
+      let mut scheduler = Scheduler::new(ti, &tick, &fsm, || {});
+      scheduler.start();
+
+      scheduler.switch();
+
+      assert_that(scheduler.current_task_index(), is(equal_to(1u8)));
+    }
+
+    it "wraps over to first task when all tasks are done" {
+      let mut scheduler = Scheduler::new(ti, &tick, &fsm, || {});
+      scheduler.start();
+
+      scheduler.switch();
+      scheduler.switch();
+
+      assert_that(scheduler.current_task_index(), is(equal_to(0u8)));
+    }
+
+    it "enables systick timer on start" {
+      let mut scheduler = Scheduler::new(ti, &tick, &fsm, || {});
+      scheduler.start();
+
+      assert_that(tick.started.get(), is(equal_to(true)));
+    }
+
+    it "loads first task stack pointer" {
+      let mut scheduler = Scheduler::new(ti, &tick, &fsm, || {});
+      scheduler.start();
+
+      assert_that(fsm.sp.get(), is(equal_to(100u32)));
+    }
+
+    it "saves stack pointer to current task on switch" {
+      let mut scheduler = Scheduler::new(ti, &tick, &fsm, || {});
+      scheduler.start();
+
+      fsm.sp.set(110);
+      scheduler.switch();
+
+      assert_that(scheduler.index().tasks[0].stack_start, is(equal_to(110u32)));
+    }
+
+    it "loads stack pointer to next task on switch" {
+      let mut scheduler = Scheduler::new(ti, &tick, &fsm, || {});
+      scheduler.start();
+
+      scheduler.switch();
+
+      assert_that(fsm.sp.get(), is(equal_to(200u32)));
+    }
+  )
+}

src/os/sched/stack.rs

@@ -0,0 +1,26 @@
+// Zinc, the bare metal stack for rust.
+// Copyright 2014 Vladimir "farcaller" Pouzanov <[email protected]>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// Tasks stack management.
+
+/// StackManager provides scheduler with interface to manage task-specific stack
+/// pointer.
+pub trait StackManager {
+  /// Returns stack pointer for currently scheduled task.
+  fn get_task_stack_pointer(&self) -> u32;
+
+  /// Sets stack pointer for currently scheduled task.
+  fn set_task_stack_pointer(&self, sp: u32);
+}

src/os/sched/task.rs

@@ -0,0 +1,34 @@
+// Zinc, the bare metal stack for rust.
+// Copyright 2014 Vladimir "farcaller" Pouzanov <[email protected]>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use core::kinds::marker;
+
+pub enum State {
+  Runnable
+}
+
+pub struct Task {
+  pub state: State,
+  pub stack_start: u32,
+  pub stack_end: u32,
+}
+
+#[packed]
+pub struct TasksIndex<'a> {
+  pub tasks: &'a mut [Task],
+  pub current_task_index: u8,
+
+  pub no_copy: marker::NoCopy,
+}

src/zinc/hal/mod.rs

@@ -37,3 +37,4 @@ pub mod spi;
 pub mod stack;
 pub mod timer;
 pub mod uart;
+pub mod systick;

src/zinc/lib.rs

@@ -48,7 +48,9 @@ extern crate core;
 extern crate rlibc;
 
 #[cfg(test)] #[phase(plugin,link)] extern crate std;
+#[cfg(test)] #[phase(plugin,link)] extern crate shiny;
 #[cfg(test)] extern crate native;
+#[cfg(test)] extern crate hamcrest;
 #[phase(plugin)] extern crate macro_ioreg;
 
 pub mod drivers;

src/zinc/os/mod.rs

@@ -20,9 +20,9 @@ This module is a higher level abstraction over hardware than hal. It might be
 incompatible direct hal usage in some cases.
 */
 
-// pub mod debug;
 pub mod syscall;
 #[cfg(cfg_multitasking)] pub mod task;
 pub mod mutex;
 pub mod cond_var;
 pub mod debug;
+pub mod sched;