Fix race condition during iteration through modules (#139283) #139862
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@llvm/pr-subscribers-lldb Author: None (nd) ChangesLock ensures modules don't change during iteration. Full diff: https://github.com/llvm/llvm-project/pull/139862.diff 1 Files Affected:
diff --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
index 7f61f8689fb95..485b49aeb64b4 100644
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -1510,6 +1510,7 @@ bool Target::IgnoreWatchpointByID(lldb::watch_id_t watch_id,
}
ModuleSP Target::GetExecutableModule() {
+ std::lock_guard<std::recursive_mutex> guard(m_images.GetMutex());
// search for the first executable in the module list
for (size_t i = 0; i < m_images.GetSize(); ++i) {
ModuleSP module_sp = m_images.GetModuleAtIndex(i);
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lldb/source/Target/Target.cpp
Outdated
| @@ -1510,6 +1510,7 @@ bool Target::IgnoreWatchpointByID(lldb::watch_id_t watch_id, | ||
| } | ||
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| ModuleSP Target::GetExecutableModule() { | ||
| std::lock_guard<std::recursive_mutex> guard(m_images.GetMutex()); |
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Let's use the Modules() iterable which allows us to use a for-based loop and does the locking for us:
// Search for the first executable in the module list.
for (ModuleSP module_sp : m_images.Modules()) {
lldb_private::ObjectFile *obj = module_sp->GetObjectFile();
Use of ModuleIterable ensures modules don't change during iteration.
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Sorry, I haven't read the LLVM GitHub user guide before submitting the PR and didn't realize that force pushes are to be avoided. Please let me know if I need to rework the request somehow. |
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This is a simple PR, so it's not an issue. The patch gets squashed&rebased anyway. The problem is that with complex, long-running reviews, force-pushes tend to lose all of the comments on the PR. |
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@nd Congratulations on having your first Pull Request (PR) merged into the LLVM Project! Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR. Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues. How to do this, and the rest of the post-merge process, is covered in detail here. If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again. If you don't get any reports, no action is required from you. Your changes are working as expected, well done! |
Lock ensures modules don't change during iteration.