[Lldb-commits] [lldb] 910353c - When calculating the "currently selected thread" in

[Jim Ingham via lldb-commits]

Author: Jim Ingham
Date: 2021-07-27T13:38:09-07:00
New Revision: 910353c1048e5efac64b639a65b4d968aba3aa81

URL: https://github.com/llvm/llvm-project/commit/910353c1048e5efac64b639a65b4d968aba3aa81
DIFF: https://github.com/llvm/llvm-project/commit/910353c1048e5efac64b639a65b4d968aba3aa81.diff

LOG: When calculating the "currently selected thread" in
Process::HandleStateChangedEvent, we check whether a thread stopped
for eStopReasonSignal is stopped for a signal that's currently set to
"no-stop". If it is, then we don't set that thread as the currently
selected thread.

But that only happens in the part of the algorithm that's handling the
case where the previously selected thread has no stop reason. Since we
want to keep on a thread as long as it is doing something interesting,
we always prefer the current thread. That's almost right, but we
forgot to check whether the previously selected thread stopped with an
eStopReasonSignal for a "no-stop" signal. If it did, then we shouldn't
select it.

This patch adds that check. I can't figure out a good way to test
this. This is the sort of thing that Ismail's scripted process plugin
will make easy once it is a real boy. But figuring out how to do this
in a real process is not trivial.

Differential Revision: https://reviews.llvm.org/D106712

Added: 
    

Modified: 
    lldb/source/Target/Process.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index 5cd739efe53a..8ecc66b592ea 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -777,13 +777,30 @@ bool Process::HandleProcessStateChangedEvent(const EventSP &event_sp,
         ThreadSP curr_thread(thread_list.GetSelectedThread());
         ThreadSP thread;
         StopReason curr_thread_stop_reason = eStopReasonInvalid;
-        if (curr_thread) {
+        bool prefer_curr_thread = false;
+        if (curr_thread && curr_thread->IsValid()) {
           curr_thread_stop_reason = curr_thread->GetStopReason();
+          switch (curr_thread_stop_reason) {
+          case eStopReasonNone:
+          case eStopReasonInvalid:
+            // Don't prefer the current thread if it didn't stop for a reason.
+            break;
+          case eStopReasonSignal: {
+            // We need to do the same computation we do for other threads
+            // below in case the current thread happens to be the one that
+            // stopped for the no-stop signal.
+            uint64_t signo = curr_thread->GetStopInfo()->GetValue();
+            if (process_sp->GetUnixSignals()->GetShouldStop(signo))
+              prefer_curr_thread = true;
+          } break;
+          default:
+            prefer_curr_thread = true;
+            break;
+          }
           curr_thread_stop_info_sp = curr_thread->GetStopInfo();
         }
-        if (!curr_thread || !curr_thread->IsValid() ||
-            curr_thread_stop_reason == eStopReasonInvalid ||
-            curr_thread_stop_reason == eStopReasonNone) {
+
+        if (!prefer_curr_thread) {
           // Prefer a thread that has just completed its plan over another
           // thread as current thread.
           ThreadSP plan_thread;