Revert "wifi: mt76: Disable napi when removing device"

This reverts commit 13b7e6a96a005c656d38f3da51581deaf9866375.

That commit made mt76_dma_cleanup() disable every RX NAPI instance before
deleting it, to silence WARNs in __netif_napi_del_locked() and
page_pool_disable_direct_recycling() seen when unloading mt7915e with an
MT7916.

On mt7921e and mt7925e the same instances are already disabled earlier,
in mt7921e_unregister_device() and mt7925e_unregister_device(), which
only afterwards call mt792x_dma_cleanup() -> mt76_dma_cleanup().  Each
instance is therefore disabled twice, and napi_disable() is not
idempotent: on return it leaves NAPIF_STATE_SCHED and NAPIF_STATE_NPSVC
set, so the second call spins in usleep_range() forever, waiting for bits
that nobody will clear.

mt7921_pci_shutdown() and mt7925_pci_shutdown() reuse the remove path, so
this is hit on every reboot, poweroff and module unload.  It is silent:
the stuck task keeps sleeping and rescheduling, so neither the hung task
detector nor the lockup detectors fire, and the last line on the console
is "systemd-shutdown[1]: Rebooting."

  task:modprobe        state:D stack:25720 pid:7954  tgid:7954
  Call Trace:
   <TASK>
   __schedule+0x11b8/0x26d0
   schedule+0xe7/0x2f0
   schedule_hrtimeout_range_clock+0x218/0x330
   usleep_range_state+0x133/0x1b0
   napi_disable_locked+0x37d/0x5f0
   napi_disable+0x43/0x80
   mt76_dma_cleanup+0x2b4/0x860 [mt76]
   mt7921_pci_remove+0x17f/0x350 [mt7921e]
   pci_device_remove+0xb6/0x1e0
   device_release_driver_internal+0x38d/0x540
   driver_detach+0xd0/0x1b0
   bus_remove_driver+0x127/0x2d0
   pci_unregister_driver+0x2a/0x280
   __do_sys_delete_module+0x36a/0x5b0
   do_syscall_64+0x11c/0x6d0
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
   </TASK>

Dropping the two driver-side loops instead was tried and rejected: with
them gone, the RX poll can reach mt76_token_release() via
PKT_TYPE_TXRX_NOTIFY and mt7921_mac_tx_free() while
mt76_connac2_tx_token_put() is running idr_destroy(&dev->token) outside
token_lock, which is a use-after-free rather than a hang [1].

Revert for now, so that reboot, poweroff and module unload work again.
The WARNs on mt7915e are a less severe problem than an unbootable
machine, and fixing them belongs in the drivers that delete the NAPI
instances, where each one can pick a point that is safe for its own
teardown order, rather than in the shared mt76_dma_cleanup().

[ This is the "landing soonish" known regression fix mentioned in the
  previous networking merge commit       - Linus ]

Reported-by: Bert Karwatzki <spasswolf@web.de>
Closes: https://lore.kernel.org/all/20260724151419.26014-1-spasswolf@web.de/
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221818
Link: https://lore.kernel.org/all/20260730050428.GA73812@sol/
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Acked-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
Fixes: 13b7e6a96a00 ("wifi: mt76: Disable napi when removing device")
Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/net/wireless/mediatek/mt76/dma.c b/drivers/net/wireless/mediatek/mt76/dma.c
index 322041859217463422c677378b1f4fa053f96599..f8c2fe5f2f58772c39719fc97e8e8d721613cf28 100644 (file)
--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -1189,10 +1189,7 @@ void mt76_dma_cleanup(struct mt76_dev *dev)
        mt76_for_each_q_rx(dev, i) {
                struct mt76_queue *q = &dev->q_rx[i];
 
-               if (!mt76_queue_is_wed_rro(q)) {
-                       napi_disable(&dev->napi[i]);
-                       netif_napi_del(&dev->napi[i]);
-               }
+               netif_napi_del(&dev->napi[i]);
                mt76_dma_rx_cleanup(dev, q);
 
                page_pool_destroy(q->page_pool);