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test_bank_forks_new_rw_arc_memory_leak should test hard fork count, rather than looping until OOM #8585

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Merged
roryharr merged 2 commits into from
Oct 21, 2025
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test_bank_forks_new_rw_arc_memory_leak should test hard fork count, rather than looping until OOM #8585

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test_bank_forks_new_rw_arc_memory_leak should test hard fork count, r…
roryharr Oct 20, 2025
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Updating test description
roryharr Oct 21, 2025
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23 changes: 19 additions & 4 deletions runtime/src/bank_forks.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -727,12 +727,27 @@ mod tests {
solana_vote_program::vote_state::BlockTimestamp,
};

// This test verifies that BankForks::new_rw_arc() doesn't create a reference cycle.
//
// Before PR #1893, there was a cycle:
// Arc<RwLock<BankForks>> → Bank → ProgramCache → Arc<RwLock<BankForks>>
//
// This happened because new_rw_arc() called:
// root_bank.set_fork_graph_in_program_cache(bank_forks.clone())
//
// The fix changed it to use a Weak reference:
// root_bank.set_fork_graph_in_program_cache(Arc::downgrade(&bank_forks))
//
// Breaking the cycle:
// Arc<RwLock<BankForks>> → Bank → ProgramCache → Weak<RwLock<BankForks>>
//
// Without the fix: strong_count == 2 (the clone creates an extra strong ref)
// With the fix: strong_count == 1 (only the returned Arc holds a strong ref)
#[test]
fn test_bank_forks_new_rw_arc_memory_leak() {
for _ in 0..1000 {
let GenesisConfigInfo { genesis_config, .. } = create_genesis_config(10_000);
BankForks::new_rw_arc(Bank::new_for_tests(&genesis_config));
}
let GenesisConfigInfo { genesis_config, .. } = create_genesis_config(10_000);
let bank_forks = BankForks::new_rw_arc(Bank::new_for_tests(&genesis_config));
assert_eq!(Arc::strong_count(&bank_forks), 1);
}

#[test]
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