ConditionVariable is a thin wrapper over the pthread_cond_* APIs, just
as Mutex is a wrapper over pthread_mutex.
Because ConditionVariable might want to wait on a high-level Mutex, it
needs to be friends with it.
Core::deferred_invoke is a way of executing an action after previously
queued events have been processed. It removes the requirement of
having/being a Core::Object subclass in order to defer invocation
through Core::Object::deferred_invoke.
Core::Object::deferred_invoke now delegates to Core::deferred_invoke.
The version with the Object& argument is still present but will be
removed in the following commits.
This commit additionally fixes a new places where the
DeferredInvocationEvent was dispatched to the event loop directly, and
replaces them with the Core::deferred_invoke equivalent.
Now that pthread_cond_t works correctly thanks to Sergey, we can use
them to wake up the BackgroundAction worker thread instead of making
a Unix pipe. :^)
This class was previously a spinlock that would call sys$donate()
to donate its timeslice to whichever thread was holding the lock.
Now that pthread_mutex_t has a fast path, let's implement Lock on top
of that instead and get rid of the last remaining user of sys$donate().
We need to move the result out of the BackgroundAction object before
posting the completion callback as there is a chance the
BackgroundAction instance gets freed before the event loop runs our
callback.
Fixes#7641
The worker thread used for BackgroundAction was going to sleep for
1 second at a time (when there was nothing to do.) This made using
background actions for anything interactive quite unresponsive since
you had to wait up to 1 second before it even started on your task.
We now use a simple Unix pipe to signal the worker thread that a new
work item is available.
This makes Assistant way more responsive when typing. :^)
Sometimes you don't care about `joining()` the result of a thread. The
underlying pthread implementation already existed for detaching and
now we expose it to the higher level API.
