Fix lock inversion in txg_sync_thread()

This patch fixes a lock inversion issue in txg_sync_thread() where
the code would attempt hold the spa config lock as a reader while
holding tx->tx_sync_lock. This races with spa_vdev_remove() which
attempts to hold the tx->tx_sync_lock to assign a new tx (via
spa_history_log_internal()) while holding the spa config lock as a
writer.

Reviewed-by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Co-authored-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #8010
This commit is contained in:
Tom Caputi 2018-10-16 17:00:55 -04:00 committed by Brian Behlendorf
parent ab4c009e3d
commit a783dd9684

View File

@ -562,22 +562,22 @@ txg_sync_thread(void *arg)
tx->tx_quiesced_txg = 0; tx->tx_quiesced_txg = 0;
tx->tx_syncing_txg = txg; tx->tx_syncing_txg = txg;
DTRACE_PROBE2(txg__syncing, dsl_pool_t *, dp, uint64_t, txg); DTRACE_PROBE2(txg__syncing, dsl_pool_t *, dp, uint64_t, txg);
txg_stat_t *ts = spa_txg_history_init_io(spa, txg, dp);
cv_broadcast(&tx->tx_quiesce_more_cv); cv_broadcast(&tx->tx_quiesce_more_cv);
dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n", dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting); txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
mutex_exit(&tx->tx_sync_lock); mutex_exit(&tx->tx_sync_lock);
txg_stat_t *ts = spa_txg_history_init_io(spa, txg, dp);
start = ddi_get_lbolt(); start = ddi_get_lbolt();
spa_sync(spa, txg); spa_sync(spa, txg);
delta = ddi_get_lbolt() - start; delta = ddi_get_lbolt() - start;
spa_txg_history_fini_io(spa, ts);
mutex_enter(&tx->tx_sync_lock); mutex_enter(&tx->tx_sync_lock);
tx->tx_synced_txg = txg; tx->tx_synced_txg = txg;
tx->tx_syncing_txg = 0; tx->tx_syncing_txg = 0;
DTRACE_PROBE2(txg__synced, dsl_pool_t *, dp, uint64_t, txg); DTRACE_PROBE2(txg__synced, dsl_pool_t *, dp, uint64_t, txg);
spa_txg_history_fini_io(spa, ts);
cv_broadcast(&tx->tx_sync_done_cv); cv_broadcast(&tx->tx_sync_done_cv);
/* /*