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MDEV-26864 Race condition between transaction commit and undo log truncation

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trx_commit_in_memory(): Do not release the rseg reference before
trx_undo_commit_cleanup() has been invoked and the current transaction
is truly done with the rollback segment. The purpose of the reference
count is to prevent data races with trx_purge_truncate_history().

This is based on
mysql/mysql-server@ac79aa1522.
This commit is contained in:
Marko Mäkelä 2021-10-21 12:29:33 +03:00
parent 8ce8c269f4
commit c484a358c8
1 changed files with 10 additions and 6 deletions
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16
storage/innobase/trx/trx0trx.cc
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@ -1775,12 +1775,7 @@ trx_commit_in_memory(
ut_ad(!trx->rsegs.m_redo.update_undo);
if (trx_rseg_t* rseg = trx->rsegs.m_redo.rseg) {
mutex_enter(&rseg->mutex);
ut_ad(rseg->trx_ref_count > 0);
--rseg->trx_ref_count;
mutex_exit(&rseg->mutex);
if (ut_d(trx_rseg_t* rseg =) trx->rsegs.m_redo.rseg) {
if (trx_undo_t*& insert = trx->rsegs.m_redo.insert_undo) {
ut_ad(insert->rseg == rseg);
trx_undo_commit_cleanup(insert, false);
@ -1849,6 +1844,15 @@ trx_commit_in_memory(
ut_ad(!trx->rsegs.m_noredo.undo);
/* Only after trx_undo_commit_cleanup() it is safe to release
our rseg reference. */
if (trx_rseg_t* rseg = trx->rsegs.m_redo.rseg) {
mutex_enter(&rseg->mutex);
ut_ad(rseg->trx_ref_count > 0);
--rseg->trx_ref_count;
mutex_exit(&rseg->mutex);
}
/* Free all savepoints, starting from the first. */
trx_named_savept_t* savep = UT_LIST_GET_FIRST(trx->trx_savepoints);