[PATCH 6.18 47/83] igb: remove napi_synchronize() in igb_down()

Greg Kroah-Hartman
2026-04-13T16:10:14Z

From: Alex Dvoretsky <advoretsky@gmail.com>

commit b1e067240379f950a0022208e0685f3465c211cb upstream.

When an AF_XDP zero-copy application terminates abruptly (e.g., kill -9),
the XSK buffer pool is destroyed but NAPI polling continues.
igb_clean_rx_irq_zc() repeatedly returns the full budget, preventing
napi_complete_done() from clearing NAPI_STATE_SCHED.

igb_down() calls napi_synchronize() before napi_disable() for each queue
vector. napi_synchronize() spins waiting for NAPI_STATE_SCHED to clear,
which never happens. igb_down() blocks indefinitely, the TX watchdog
fires, and the TX queue remains permanently stalled.

napi_disable() already handles this correctly: it sets NAPI_STATE_DISABLE.
After a full-budget poll, __napi_poll() checks napi_disable_pending(). If
set, it forces completion and clears NAPI_STATE_SCHED, breaking the loop
that napi_synchronize() cannot.

napi_synchronize() was added in commit 41f149a285da ("igb: Fix possible
panic caused by Rx traffic arrival while interface is down").
napi_disable() provides stronger guarantees: it prevents further
scheduling and waits for any active poll to exit.
Other Intel drivers (ixgbe, ice, i40e) use napi_disable() without a
preceding napi_synchronize() in their down paths.

Remove redundant napi_synchronize() call and reorder napi_disable()
before igb_set_queue_napi() so the queue-to-NAPI mapping is only
cleared after polling has fully stopped.

Fixes: 2c6196013f84 ("igb: Add AF_XDP zero-copy Rx support")
Cc: stable@vger.kernel.org
Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Alex Dvoretsky <advoretsky@gmail.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Patryk Holda <patryk.holda@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/intel/igb/igb_main.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2203,9 +2203,8 @@ void igb_down(struct igb_adapter *adapte

for (i = 0; i < adapter->num_q_vectors; i++) {
if (adapter->q_vector[i]) {
- napi_synchronize(&adapter->q_vector[i]->napi);
- igb_set_queue_napi(adapter, i, NULL);
napi_disable(&adapter->q_vector[i]->napi);
+ igb_set_queue_napi(adapter, i, NULL);
}
}