pub async fn yield_now()
Yields execution back to the Tokio runtime.
A task yields by awaiting on
yield_now(), and may resume when that future
completes (with no output.) The current task will be re-added as a pending
task at the back of the pending queue. Any other pending tasks will be
scheduled. No other waking is required for the task to continue.
See also the usage example in the task module.
This function may not yield all the way up to the executor if there are any
special combinators above it in the call stack. For example, if a
tokio::select! has another branch complete during the same poll as the
yield_now(), then the yield is not propagated all the way up to the
It is generally not guaranteed that the runtime behaves like you expect it
to when deciding which task to schedule next after a call to
In particular, the runtime may choose to poll the task that just ran
yield_now() again immediately without polling any other tasks first. For
example, the runtime will not drive the IO driver between every poll of a
task, and this could result in the runtime polling the current task again
immediately even if there is another task that could make progress if that
other task is waiting for a notification from the IO driver.
In general, changes to the order in which the runtime polls tasks is not considered a breaking change, and your program should be correct no matter which order the runtime polls your tasks in.