[lldb] Protect the selected frame idx in StackFrameList #150718
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@llvm/pr-subscribers-lldb Author: Jonas Devlieghere (JDevlieghere) ChangesProtected m_selected_frame_idx using the StackFrameList mutex. All other readers and writes already take the m_list_mutex so we can use that to protect concurrent access. Full diff: https://github.com/llvm/llvm-project/pull/150718.diff 1 Files Affected:
diff --git a/lldb/source/Target/StackFrameList.cpp b/lldb/source/Target/StackFrameList.cpp
index 16cd2548c2784..4c5f41f292e56 100644
--- a/lldb/source/Target/StackFrameList.cpp
+++ b/lldb/source/Target/StackFrameList.cpp
@@ -783,6 +783,8 @@ void StackFrameList::SelectMostRelevantFrame() {
uint32_t
StackFrameList::GetSelectedFrameIndex(SelectMostRelevant select_most_relevant) {
+ std::shared_lock<std::shared_mutex> guard(m_list_mutex);
+
if (!m_selected_frame_idx && select_most_relevant)
SelectMostRelevantFrame();
if (!m_selected_frame_idx) {
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Speculative fix for the crashes I'm seeing on the Linux bots in #148994. Both backtraces show the default event handler thread in |
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This means that we are holding the stack frame list mutex over the call to SelectMostRelevantFrame. But SelectMostRelevantFrame can call into arbitrary Python - since that's where the FrameRecognizers are triggered. These mutexes aren't recursive so if the Frame Recognizer does anything that needs the frame mutex, this is going to deadlock. |
Protected m_selected_frame_idx using a mutex.
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Yeah, I came to the same conclusion. I ended going with a separate, recursive mutex. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/11/builds/20409 Here is the relevant piece of the build log for the reference |
mahesh-attarde
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Jul 28, 2025
Protected m_selected_frame_idx with a mutex. To avoid deadlocks, always acquire m_selected_frame_mutex after m_list_mutex. I'm using a recursive mutex because GetSelectedFrameIndex may indirectly call SetSelectedFrame.
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Protected m_selected_frame_idx using the StackFrameList mutex. All other readers and writes already take the m_list_mutex so we can use that to protect concurrent access.