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    SubjectRe: [PATCH 5.13] mwifiex: bring down link before deleting interface
    On 2021-05-15 04:42, Brian Norris wrote:
    > We can deadlock when rmmod'ing the driver or going through firmware
    > reset, because the cfg80211_unregister_wdev() has to bring down the
    > link
    > for us, ... which then grab the same wiphy lock.
    >
    > nl80211_del_interface() already handles a very similar case, with a
    > nice
    > description:
    >
    > /*
    > * We hold RTNL, so this is safe, without RTNL opencount cannot
    > * reach 0, and thus the rdev cannot be deleted.
    > *
    > * We need to do it for the dev_close(), since that will call
    > * the netdev notifiers, and we need to acquire the mutex there
    > * but don't know if we get there from here or from some other
    > * place (e.g. "ip link set ... down").
    > */
    > mutex_unlock(&rdev->wiphy.mtx);
    > ...
    >
    > Do similarly for mwifiex teardown, by ensuring we bring the link down
    > first.
    >
    > Sample deadlock trace:
    >
    > [ 247.103516] INFO: task rmmod:2119 blocked for more than 123 seconds.
    > [ 247.110630] Not tainted 5.12.4 #5
    > [ 247.115796] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
    > disables this message.
    > [ 247.124557] task:rmmod state:D stack: 0 pid: 2119
    > ppid: 2114 flags:0x00400208
    > [ 247.133905] Call trace:
    > [ 247.136644] __switch_to+0x130/0x170
    > [ 247.140643] __schedule+0x714/0xa0c
    > [ 247.144548] schedule_preempt_disabled+0x88/0xf4
    > [ 247.149714] __mutex_lock_common+0x43c/0x750
    > [ 247.154496] mutex_lock_nested+0x5c/0x68
    > [ 247.158884] cfg80211_netdev_notifier_call+0x280/0x4e0 [cfg80211]
    > [ 247.165769] raw_notifier_call_chain+0x4c/0x78
    > [ 247.170742] call_netdevice_notifiers_info+0x68/0xa4
    > [ 247.176305] __dev_close_many+0x7c/0x138
    > [ 247.180693] dev_close_many+0x7c/0x10c
    > [ 247.184893] unregister_netdevice_many+0xfc/0x654
    > [ 247.190158] unregister_netdevice_queue+0xb4/0xe0
    > [ 247.195424] _cfg80211_unregister_wdev+0xa4/0x204 [cfg80211]
    > [ 247.201816] cfg80211_unregister_wdev+0x20/0x2c [cfg80211]
    > [ 247.208016] mwifiex_del_virtual_intf+0xc8/0x188 [mwifiex]
    > [ 247.214174] mwifiex_uninit_sw+0x158/0x1b0 [mwifiex]
    > [ 247.219747] mwifiex_remove_card+0x38/0xa0 [mwifiex]
    > [ 247.225316] mwifiex_pcie_remove+0xd0/0xe0 [mwifiex_pcie]
    > [ 247.231451] pci_device_remove+0x50/0xe0
    > [ 247.235849] device_release_driver_internal+0x110/0x1b0
    > [ 247.241701] driver_detach+0x5c/0x9c
    > [ 247.245704] bus_remove_driver+0x84/0xb8
    > [ 247.250095] driver_unregister+0x3c/0x60
    > [ 247.254486] pci_unregister_driver+0x2c/0x90
    > [ 247.259267] cleanup_module+0x18/0xcdc [mwifiex_pcie]
    >
    > Fixes: a05829a7222e ("cfg80211: avoid holding the RTNL when calling the
    > driver")
    > Cc: stable@vger.kernel.org
    > Link:
    > https://lore.kernel.org/linux-wireless/98392296-40ee-6300-369c-32e16cff3725@gmail.com/
    > Link:
    > https://lore.kernel.org/linux-wireless/ab4d00ce52f32bd8e45ad0448a44737e@bewaar.me/
    > Reported-by: Maximilian Luz <luzmaximilian@gmail.com>
    > Reported-by: Dave Olsthoorn <dave@bewaar.me>

    Thanks!

    The firmware still seems to crash quicker than previously, but that's a
    unrelated problem.

    Tested-by: Dave Olsthoorn <dave@bewaar.me>

    > Cc: Johannes Berg <johannes@sipsolutions.net>
    > Signed-off-by: Brian Norris <briannorris@chromium.org>
    > ---
    > drivers/net/wireless/marvell/mwifiex/main.c | 13 ++++++++++---
    > 1 file changed, 10 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/net/wireless/marvell/mwifiex/main.c
    > b/drivers/net/wireless/marvell/mwifiex/main.c
    > index 529dfd8b7ae8..17399d4aa129 100644
    > --- a/drivers/net/wireless/marvell/mwifiex/main.c
    > +++ b/drivers/net/wireless/marvell/mwifiex/main.c
    > @@ -1445,11 +1445,18 @@ static void mwifiex_uninit_sw(struct
    > mwifiex_adapter *adapter)
    > if (!priv)
    > continue;
    > rtnl_lock();
    > - wiphy_lock(adapter->wiphy);
    > if (priv->netdev &&
    > - priv->wdev.iftype != NL80211_IFTYPE_UNSPECIFIED)
    > + priv->wdev.iftype != NL80211_IFTYPE_UNSPECIFIED) {
    > + /*
    > + * Close the netdev now, because if we do it later, the
    > + * netdev notifiers will need to acquire the wiphy lock
    > + * again --> deadlock.
    > + */
    > + dev_close(priv->wdev.netdev);
    > + wiphy_lock(adapter->wiphy);
    > mwifiex_del_virtual_intf(adapter->wiphy, &priv->wdev);
    > - wiphy_unlock(adapter->wiphy);
    > + wiphy_unlock(adapter->wiphy);
    > + }
    > rtnl_unlock();
    > }

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