[lldb] Don't ask for QOS_CLASS_UNSPECIFIED queue in TestQueues

[teemperor]

Summary

TestQueues is curiously failing for me as my queue for QOS_CLASS_UNSPECIFIED
is named "Utility" and not "User Initiated" or "Default". While debugging, this
I noticed that this test isn't actually using this API right from what I understand. The API documentation
for dispatch_get_global_queue specifies for the parameter: "You may specify the value
QOS_CLASS_USER_INTERACTIVE, QOS_CLASS_USER_INITIATED, QOS_CLASS_UTILITY, or QOS_CLASS_BACKGROUND."

QOS_CLASS_UNSPECIFIED isn't listed as one of the supported values. swift-corelibs-libdispatch
even checks for this value and returns a DISPATCH_BAD_INPUT. The
libdispatch shipped on macOS seems to also check for QOS_CLASS_UNSPECIFIED and seems to
instead cause a "client crash", but somehow this doesn't trigger in this test and instead we just
get whatever queue

This patch just removes that part of the test as it appears the code is just incorrect.

[teemperor]

Some links to the swift sources:

1. The dispatch_get_global_queue source: https://github.com/apple/swift-corelibs-libdispatch/blob/f7a0cbb/src/init.c#L365
2. This passes the input QoS to _dispatch_qos_from_queue_priority : https://github.com/apple/swift-corelibs-libdispatch/blob/f7a0cbb761e49df0b1a114b0537ae03aacf2519e/src/shims/priority.h#L173
3. Which then calls _dispatch_qos_from_qos_class which defines DISPATCH_QOS_UNSPECIFIED as an error value: https://github.com/apple/swift-corelibs-libdispatch/blob/f7a0cbb761e49df0b1a114b0537ae03aacf2519e/src/shims/priority.h#L143
4. That all returns and when the calculated QoS is "UNSPECIFIED" we should hit the error case here and return "BAD_INPUT": https://github.com/apple/swift-corelibs-libdispatch/blob/f7a0cbb/src/init.c#L381

[jasonmolenda]

LGTM, that call to dispatch_get_global_queue QOS_CLASS_UNSPECIFIED does not look valid.

lldb/test/API/macosx/queues/TestQueues.py

def queues(self):
 
         # We have threads running with all the different dispatch QoS service
         # levels - find those threads and check that we can get the correct
         # QoS name for each of them.
 
         user_initiated_thread = lldb.SBThread()
         user_interactive_thread = lldb.SBThread()
         utility_thread = lldb.SBThread()
-        unspecified_thread = lldb.SBThread()
         background_thread = lldb.SBThread()
         for th in process.threads:
             if th.GetName() == "user initiated QoS":
                 user_initiated_thread = th
             if th.GetName() == "user interactive QoS":
                 user_interactive_thread = th
             if th.GetName() == "utility QoS":
                 utility_thread = th
-            if th.GetName() == "unspecified QoS":
-                unspecified_thread = th
             if th.GetName() == "background QoS":
                 background_thread = th
 
         self.assertTrue(
             user_initiated_thread.IsValid(),
             "Found user initiated QoS thread")
         self.assertTrue(
             user_interactive_thread.IsValid(),
             "Found user interactive QoS thread")
         self.assertTrue(utility_thread.IsValid(), "Found utility QoS thread")
         self.assertTrue(
-            unspecified_thread.IsValid(),
-            "Found unspecified QoS thread")
-        self.assertTrue(
             background_thread.IsValid(),
             "Found background QoS thread")
 
         stream = lldb.SBStream()
         self.assertTrue(
             user_initiated_thread.GetInfoItemByPathAsString(
                 "requested_qos.printable_name",
                 stream),
def queues(self):
                 "requested_qos.printable_name",
                 stream),
             "Get QoS printable string for utility QoS thread")
         self.assertEqual(
             stream.GetData(), "Utility",
             "utility QoS thread name is valid")
         stream.Clear()
         self.assertTrue(
-            unspecified_thread.GetInfoItemByPathAsString(
-                "requested_qos.printable_name",
-                stream),
-            "Get QoS printable string for unspecified QoS thread")
-        qosName = stream.GetData()
-        self.assertTrue(
-            qosName == "User Initiated" or qosName == "Default",
-            "unspecified QoS thread name is valid: " + str(qosName))
-        stream.Clear()
-        self.assertTrue(
             background_thread.GetInfoItemByPathAsString(
                 "requested_qos.printable_name",
                 stream),
             "Get QoS printable string for background QoS thread")
         self.assertEqual(
             stream.GetData(), "Background",
             "background QoS thread name is valid")
 

lldb/test/API/macosx/queues/main.c

dispatch_async (dispatch_get_global_queue(QOS_CLASS_UTILITY, 0), ^{
                 sleep (10);
       });
     dispatch_async (dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0), ^{
             pthread_setname_np ("background QoS");
             atomic_fetch_add(&thread_count, 1);
             while (1)
                 sleep (10);
       });
-    dispatch_async (dispatch_get_global_queue(QOS_CLASS_UNSPECIFIED, 0), ^{
-            pthread_setname_np ("unspecified QoS");
-            atomic_fetch_add(&thread_count, 1);
-            while (1)
-                sleep (10);
-      });
 
     // Unfortunately there is no pthread_barrier on darwin.
-    while ((atomic_load(&thread_count) < 13) || (finished_enqueueing_work == 0))
+    while ((atomic_load(&thread_count) < 12) || (finished_enqueueing_work == 0))
         sleep (1);
 
     stopper ();
 }