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Fixing 3-cycle possible deadlock active_transactions -> election -> mdb_write_mutex. This was introduced with final votes and is alliviated by releasing the election mutex before issuing a final vote which requires the database write mutex. (#3269)

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clemahieu 2021-05-10 09:49:35 +01:00 • committed by GitHub
commit 186babe0b0
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1 changed files with 9 additions and 3 deletions
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12
nano/node/election.cpp
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@ -293,7 +293,10 @@ void nano::election::confirm_if_quorum (nano::unique_lock<nano::mutex> & lock_a)
{
if (node.ledger.cache.final_votes_confirmation_canary.load () && !is_quorum.exchange (true) && node.config.enable_voting && node.wallets.reps ().voting > 0)
{
node.active.final_generator.add (root, status.winner->hash ());
auto hash = status.winner->hash ();
lock_a.unlock ();
node.active.final_generator.add (root, hash);
lock_a.lock ();
}
if (!node.ledger.cache.final_votes_confirmation_canary.load () || final_weight >= node.online_reps.delta ())
{
@ -507,10 +510,13 @@ void nano::election::generate_votes () const
{
if (node.config.enable_voting && node.wallets.reps ().voting > 0)
{
nano::lock_guard<nano::mutex> guard (mutex);
nano::unique_lock<nano::mutex> lock (mutex);
if (confirmed () || have_quorum (tally_impl ()))
{
node.active.final_generator.add (root, status.winner->hash ());
auto hash = status.winner->hash ();
lock.unlock ();
node.active.final_generator.add (root, hash);
lock.lock ();
}
else
{