SL-16220: WorkQueue::runOn() methods submit work, wait for result.

The idea is that you can call runOn(target, callable) from a (non-default)
coroutine and block that coroutine until the result becomes available.

As a safety check, we forbid calling runOn() from a thread's default
coroutine, assuming that a given thread's default coroutine is the one
servicing the relevant WorkQueue.

1 files changed, 15 insertions, 0 deletions

diff --git a/indra/llcommon/workqueue.cpp b/indra/llcommon/workqueue.cpp
index 114aeea1f3..f7ffc8233c 100644
--- a/indra/llcommon/workqueue.cpp
+++ b/indra/llcommon/workqueue.cpp
@@ -26,6 +26,11 @@
 using Mutex = LLCoros::Mutex;
 using Lock  = LLCoros::LockType;
 
+struct NotOnDftCoro: public LLException
+{
+    NotOnDftCoro(const std::string& what): LLException(what) {}
+};
+
 LL::WorkQueue::WorkQueue(const std::string& name):
     super(makeName(name))
 {
@@ -136,3 +141,13 @@ void LL::WorkQueue::error(const std::string& msg)
 {
     LL_ERRS("WorkQueue") << msg << LL_ENDL;
 }
+
+void LL::WorkQueue::checkCoroutine(const std::string& method)
+{
+    // By convention, the default coroutine on each thread has an empty name
+    // string. See also LLCoros::logname().
+    if (LLCoros::getName().empty())
+    {
+        LLTHROW(NotOnDftCoro("Do not call " + method + " from a thread's default coroutine"));
+    }
+}