From d4c1ad882973e407ff85b977f4ce5b9435451190 Mon Sep 17 00:00:00 2001 From: Tzu-Chiao Yeh Date: Mon, 24 Aug 2020 22:04:17 +0800 Subject: database/sql: fix tx stmt deadlock when rollback Tx acquires tx.closemu W-lock and then acquires stmt.closemu.W-lock to fully close the transaction and associated prepared statement. Stmt query and execution run in reverse ways - acquires stmt.closemu.R-lock and then acquires tx.closemu.R-lock to grab tx connection, which may cause deadlock. Prevent the lock is held around tx.closePrepared to ensure no deadlock happens. Fixes #40985 Change-Id: If53909822b87bce11861a6e3035ecb9476d2cd17 Reviewed-on: https://go-review.googlesource.com/c/go/+/250178 Run-TryBot: Emmanuel Odeke TryBot-Result: Go Bot Reviewed-by: Daniel Theophanes Trust: Emmanuel Odeke --- src/database/sql/sql_test.go | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'src/database/sql/sql_test.go') diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go index 762d42f54b..8ae6e1339e 100644 --- a/src/database/sql/sql_test.go +++ b/src/database/sql/sql_test.go @@ -2810,6 +2810,36 @@ func TestTxCannotCommitAfterRollback(t *testing.T) { } } +// Issue 40985 transaction statement deadlock while context cancel. +func TestTxStmtDeadlock(t *testing.T) { + db := newTestDB(t, "people") + defer closeDB(t, db) + + ctx, cancel := context.WithTimeout(context.Background(), 5*time.Millisecond) + defer cancel() + tx, err := db.BeginTx(ctx, nil) + if err != nil { + t.Fatal(err) + } + + stmt, err := tx.Prepare("SELECT|people|name,age|age=?") + if err != nil { + t.Fatal(err) + } + // Run number of stmt queries to reproduce deadlock from context cancel + for i := 0; i < 1e3; i++ { + _, err = stmt.Query(1) + if err != nil { + // Encounter ErrTxDone here is expected due to context cancel + if err != ErrTxDone { + t.Fatalf("unexpected error while executing stmt, err: %v", err) + } + break + } + } + _ = tx.Rollback() +} + // Issue32530 encounters an issue where a connection may // expire right after it comes out of a used connection pool // even when a new connection is requested. -- cgit v1.3