From cddafdcbc55a38cdbdd3dc8c58f447b22bd847ee Mon Sep 17 00:00:00 2001 From: Martin Matuska Date: Mon, 1 Aug 2011 10:34:06 -0700 Subject: [PATCH] Illumos #1313: Integer overflow in txg_delay() The function txg_delay() is used to delay txg (transaction group) threads in ZFS. The timeout value for this function is calculated using: int timeout = ddi_get_lbolt() + ticks; Later, the actual wait is performed: while (ddi_get_lbolt() < timeout && tx->tx_syncing_txg < txg-1 && !txg_stalled(dp)) (void) cv_timedwait(&tx->tx_quiesce_more_cv, &tx->tx_sync_lock, timeout - ddi_get_lbolt()); The ddi_get_lbolt() function returns current uptime in clock ticks and is typed as clock_t. The clock_t type on 64-bit architectures is int64_t. The "timeout" variable will overflow depending on the tick frequency (e.g. for 1000 it will overflow in 28.855 days). This will make the expression "ddi_get_lbolt() < timeout" always false - txg threads will not be delayed anymore at all. This leads to a slowdown in ZFS writes. The attached patch initializes timeout as clock_t to match the return value of ddi_get_lbolt(). Signed-off-by: Brian Behlendorf Issue #352 --- module/zfs/txg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/module/zfs/txg.c b/module/zfs/txg.c index 340c42ae8..d0d2b1716 100644 --- a/module/zfs/txg.c +++ b/module/zfs/txg.c @@ -506,7 +506,7 @@ void txg_delay(dsl_pool_t *dp, uint64_t txg, int ticks) { tx_state_t *tx = &dp->dp_tx; - int timeout = ddi_get_lbolt() + ticks; + clock_t timeout = ddi_get_lbolt() + ticks; /* don't delay if this txg could transition to quiesing immediately */ if (tx->tx_open_txg > txg ||