[RFC iwl-net] e1000: Hold RTNL when e1000_down can be called

From: Joe Damato
Date: Tue Oct 22 2024 - 13:22:14 EST


e1000_down calls netif_queue_set_napi, which assumes that RTNL is held.

There are a few paths for e1000_down to be called in e1000 where RTNL is
not currently being held:
- e1000_shutdown (pci shutdown)
- e1000_suspend (power management)
- e1000_reinit_locked (via e1000_reset_task delayed work)

Hold RTNL in two places to fix this issue:
- e1000_reset_task
- __e1000_shutdown (which is called from both e1000_shutdown and
e1000_suspend).

The other paths which call e1000_down seemingly hold RTNL and are OK:
- e1000_close (ndo_stop)
- e1000_change_mtu (ndo_change_mtu)

I'm submitting this is as an RFC because:
- the e1000_reinit_locked issue appears very similar to commit
21f857f0321d ("e1000e: add rtnl_lock() to e1000_reset_task"), which
fixes a similar issue in e1000e

however

- adding rtnl to e1000_reinit_locked seemingly conflicts with an
earlier e1000 commit b2f963bfaeba ("e1000: fix lockdep warning in
e1000_reset_task").

Hopefully Intel can weigh in and shed some light on the correct way to
go.

Fixes: 8f7ff18a5ec7 ("e1000: Link NAPI instances to queues and IRQs")
Reported-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
Closes: https://lore.kernel.org/netdev/8cf62307-1965-46a0-a411-ff0080090ff9@xxxxxxxxx/
Signed-off-by: Joe Damato <jdamato@xxxxxxxxxx>
---
drivers/net/ethernet/intel/e1000/e1000_main.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 4de9b156b2be..9ed99c75d59e 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -3509,7 +3509,9 @@ static void e1000_reset_task(struct work_struct *work)
container_of(work, struct e1000_adapter, reset_task);

e_err(drv, "Reset adapter\n");
+ rtnl_lock();
e1000_reinit_locked(adapter);
+ rtnl_unlock();
}

/**
@@ -5074,7 +5076,9 @@ static int __e1000_shutdown(struct pci_dev *pdev, bool *enable_wake)
usleep_range(10000, 20000);

WARN_ON(test_bit(__E1000_RESETTING, &adapter->flags));
+ rtnl_lock();
e1000_down(adapter);
+ rtnl_unlock();
}

status = er32(STATUS);

base-commit: d811ac148f0afd2f3f7e1cd7f54de8da973ec5e3
--
2.25.1