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Wed, 11 Mar 2026 13:46:22 -0700 (PDT) From: Alex Dvoretsky To: intel-wired-lan@lists.osuosl.org Cc: netdev@vger.kernel.org, maciej.fijalkowski@intel.com, aleksandr.loktionov@intel.com, anthony.l.nguyen@intel.com, przemyslaw.kitszel@intel.com, kurt@linutronix.de, stable@vger.kernel.org, Alex Dvoretsky Subject: [PATCH net v2] igb: remove napi_synchronize() in igb_down() Date: Wed, 11 Mar 2026 21:45:15 +0100 Message-ID: <20260311204620.15763-1-advoretsky@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. Fixes: 2c6196013f84 ("igb: Add AF_XDP zero-copy Rx support") Cc: stable@vger.kernel.org Signed-off-by: Alex Dvoretsky --- Thanks for the suggestion, Maciej. I tested removing napi_synchronize() and it fixes the issue cleanly — napi_disable() handles the stuck poll via NAPI_STATE_DISABLE without needing any hot-path changes. v2: - Replaced 3-patch series with single napi_synchronize() removal, per Maciej Fijalkowski's suggestion. napi_disable() handles the stuck NAPI poll via NAPI_STATE_DISABLE, making the __IGB_DOWN checks in igb_clean_rx_irq_zc() and igb_tx_timeout(), and the transition guards in igb_xdp_setup(), all unnecessary. - Tested on Intel I210 (igb) with AF_XDP zero-copy: full E2E traffic suite, graceful shutdown, and 5x kill-9 stress cycles. Zero tx_timeout events. drivers/net/ethernet/intel/igb/igb_main.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index 12e8e30d8a2d..a1b3c5e4f7d2 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -2203,7 +2203,6 @@ void igb_down(struct igb_adapter *adapter) 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); } -- 2.51.0