zephyr: work: Support showing work in Segger SystemView

If `CONFIG_SEGGER_SYSVIEW` is enabled, add a few calls to the workqueue
scheduling to record these as task switches.  There is still a problem
with the task names showing up, but this does generally show scheduled
work as separate tasks in System View.

The main issues where this lacks is that if the Zephyr scheduler
schedules something else, and then returns to the work queue, that will
be shown as being done on the work queue thread instead of the
particular work.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

zephyr-sys/build.rs

@@ -88,6 +88,7 @@ fn main() -> Result<()> {
         .allowlist_function("sys_.*")
         .allowlist_function("z_log.*")
         .allowlist_function("bt_.*")
+        .allowlist_function("SEGGER.*")
         .allowlist_item("E.*")
         .allowlist_item("K_.*")
         .allowlist_item("ZR_.*")

zephyr/src/work/futures.rs

@@ -384,6 +384,23 @@ impl<F: Future> WorkData<F> {
         unsafe {
             // SAFETY: The above Arc allocates the worker.  The code here is careful to not move it.
             k_work_poll_init(this.work.get(), Some(Self::handler));
+
+            // If we have a name, send it to Segger.
+            #[cfg(CONFIG_SEGGER_SYSTEMVIEW)]
+            {
+                let ww = &(&*this.work.get()).work;
+                if let Some(name) = name {
+                    let info = crate::raw::SEGGER_SYSVIEW_TASKINFO {
+                        TaskID: this.work.get() as ::core::ffi::c_ulong,
+                        sName: name.as_ptr(),
+                        Prio: 1,
+                        StackBase: 0,
+                        StackSize: 32,
+                    };
+                    crate::raw::SEGGER_SYSVIEW_OnTaskCreate(this.work.get() as ::core::ffi::c_ulong);
+                    crate::raw::SEGGER_SYSVIEW_SendTaskInfo(&info);
+                }
+            }
         }
 
         this
@@ -458,8 +475,16 @@ impl<F: Future> WorkData<F> {
         // SAFETY: poll requires the pointer to be pinned, in case that is needed.  We rely on the
         // Boxing of the pointer, and that our code does not move the future.
         let future = unsafe { Pin::new_unchecked(&mut this_ref.future) };
+        #[cfg(CONFIG_SEGGER_SYSTEMVIEW)]
+        unsafe {
+            crate::raw::SEGGER_SYSVIEW_OnTaskStartExec(work as u32);
+        }
         match future.poll(&mut this_ref.info.context) {
             Poll::Pending => {
+                #[cfg(CONFIG_SEGGER_SYSTEMVIEW)]
+                unsafe {
+                    crate::raw::SEGGER_SYSVIEW_OnTaskStopExec();
+                }
                 // With pending, use the timeout and events to schedule ourselves to do more work.
                 // TODO: If we want to support a real Waker, this would need to detect that, and
                 // schedule a possible wake on this no wake case.
@@ -473,6 +498,11 @@ impl<F: Future> WorkData<F> {
                 Self::submit(this).expect("Unable to schedule work");
             }
             Poll::Ready(answer) => {
+                #[cfg(CONFIG_SEGGER_SYSTEMVIEW)]
+                unsafe {
+                    crate::raw::SEGGER_SYSVIEW_OnTaskStopExec();
+                }
+                // TODO: Delete the task as well.
                 // If the spawning task is still interested in the answer, provide it.
                 if let Some(store) = this.answer.upgrade() {
                     store.place(answer);