Author: friss
Date: Wed Mar  6 13:56:14 2019
New Revision: 355555

URL: http://llvm.org/viewvc/llvm-project?rev=355555&view=rev
Log:
[debugserver] Fix IsUserReady thread filtering

Summary:
In 2010 (r118866), filtering code was added to debugserver to avoid reporting 
threads
that were "not ready to be displayed to the user". This code inspects the 
thread's
state and discards threads marked 'uninterruptible'. Turns out, this state is 
pretty
common and not only a characterisitic of 'user-readiness'. This filtering was 
tracked
down as the source of the flakiness of TestQueues and TestConcurrent* with the 
symptom
of missing threads.

We discussed with the kernel team and there should be no need for us to filter 
the
restult of task_threads(). Everything that is returned from there can be 
examined.
So I went on and tried to remove the filtering completely. This produces other 
test
failures, where we were reporting more theads than expected. Always threads 
that had
been terminated, but weren't removed from the task bookkeeping structures yet. 
Those
threads always had a PC of 0.

This patch changes the heuristic to make the filtering a little less strict and 
only
rejects threads that are 'uninteruptible' *and* have a PC of 0. This has proven 
to be
solid in my testing.

Reviewers: jasonmolenda, clayborg, jingham

Subscribers: jdoerfert, lldb-commits

Differential Revision: https://reviews.llvm.org/D58912

Modified:
    lldb/trunk/tools/debugserver/source/MacOSX/MachThread.cpp

Modified: lldb/trunk/tools/debugserver/source/MacOSX/MachThread.cpp
URL: 
http://llvm.org/viewvc/llvm-project/lldb/trunk/tools/debugserver/source/MacOSX/MachThread.cpp?rev=355555&r1=355554&r2=355555&view=diff
==============================================================================
--- lldb/trunk/tools/debugserver/source/MacOSX/MachThread.cpp (original)
+++ lldb/trunk/tools/debugserver/source/MacOSX/MachThread.cpp Wed Mar  6 
13:56:14 2019
@@ -243,7 +243,7 @@ bool MachThread::IsUserReady() {
   case TH_STATE_HALTED:
     return true;
   }
-  return false;
+  return GetPC(0) != 0;
 }
 
 struct thread_basic_info *MachThread::GetBasicInfo() {


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