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[lldb] Add try_lock to SBMutex #164109

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Merged
merged 2 commits into from
Oct 20, 2025
Merged

[lldb] Add try_lock to SBMutex #164109

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32cbb92
[lldb] Add try_lock to SBMutex
JDevlieghere Oct 18, 2025
a48b0e9
Try calling try_lock when the mutex is locked
JDevlieghere Oct 20, 2025
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4 changes: 4 additions & 0 deletions lldb/include/lldb/API/SBMutex.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,10 @@ class LLDB_API SBMutex {
/// Releases ownership of this lock.
void unlock() const;

/// Tries to lock the mutex. Returns immediately. On successful lock
/// acquisition returns true, otherwise returns false.
bool try_lock() const;

private:
// Private constructor used by SBTarget to create the Target API mutex.
// Requires a friend declaration.
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9 changes: 9 additions & 0 deletions lldb/source/API/SBMutex.cpp
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Expand Up @@ -58,3 +58,12 @@ void SBMutex::unlock() const {
if (m_opaque_sp)
m_opaque_sp->unlock();
}

bool SBMutex::try_lock() const {
LLDB_INSTRUMENT_VA(this);

if (m_opaque_sp)
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@Michael137 Michael137 Oct 18, 2025 •
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I know this is what we do in all the other methods too, but under what circumstances can this be nullptr? Isn't its lifetime at least that of the owning SBMutex?

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Yes, it's a wrapper around a std::shared_ptr<std::recursive_mutex>. It could be null when you use the constructor that takes an SBTarget that is null.

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Correct me if I'm wrong, but I don't think the aliasing constructor allows SBTarget to ever be null. After all, we're aliasing one of its members, so we always dereference it.

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Yes, you're right. If that's the case then I don't think the pointer can be null. Doesn't look like we do this in SBTarget either, but we could update the classes where that's the case to have an assert, but that would be a bigger change.

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Yea definitely out-of-scope of this PR. Adding an assert and removing the null-checks would be a nice-to-have

return m_opaque_sp->try_lock();

return false;
}
5 changes: 5 additions & 0 deletions lldb/unittests/API/SBMutexTest.cpp
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Expand Up @@ -36,11 +36,16 @@ TEST_F(SBMutexTest, LockTest) {
std::future<void> f;
{
lldb::SBMutex lock = target.GetAPIMutex();

ASSERT_TRUE(lock.try_lock());
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try_lock another time to confirm that it fails?

lock.unlock();

std::lock_guard<lldb::SBMutex> lock_guard(lock);
ASSERT_FALSE(locked.exchange(true));

f = std::async(std::launch::async, [&]() {
ASSERT_TRUE(locked);
EXPECT_FALSE(lock.try_lock());
target.BreakpointCreateByName("foo", "bar");
ASSERT_FALSE(locked);
});
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