diff options
| -rw-r--r-- | module/zfs/dmu_tx.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c index cbadcc86f..7d65e842f 100644 --- a/module/zfs/dmu_tx.c +++ b/module/zfs/dmu_tx.c @@ -925,6 +925,25 @@ dmu_tx_try_assign(dmu_tx_t *tx, uint64_t txg_how) txh = list_next(&tx->tx_holds, txh)) { dnode_t *dn = txh->txh_dnode; if (dn != NULL) { + /* + * This thread can't hold the dn_struct_rwlock + * while assigning the tx, because this can lead to + * deadlock. Specifically, if this dnode is already + * assigned to an earlier txg, this thread may need + * to wait for that txg to sync (the ERESTART case + * below). The other thread that has assigned this + * dnode to an earlier txg prevents this txg from + * syncing until its tx can complete (calling + * dmu_tx_commit()), but it may need to acquire the + * dn_struct_rwlock to do so (e.g. via + * dmu_buf_hold*()). + * + * Note that this thread can't hold the lock for + * read either, but the rwlock doesn't record + * enough information to make that assertion. + */ + ASSERT(!RW_WRITE_HELD(&dn->dn_struct_rwlock)); + mutex_enter(&dn->dn_mtx); if (dn->dn_assigned_txg == tx->tx_txg - 1) { mutex_exit(&dn->dn_mtx); |