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Subject: Re: [PATCH v5.1-rc] iwlwifi: make locking in iwl_mvm_tx_mpdu()
 BH-safe
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Jiri Kosina <jikos@kernel.org>,
        Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
        Luca Coelho <luciano.coelho@intel.com>
Cc:     Intel Linux Wireless <linuxwifi@intel.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 15 Apr 2019 13:10:45 +0200
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On Mon, 2019-04-15 at 13:03 +0200, Jiri Kosina wrote:

(FWIW, would be good to cc linux-wireless, but no need for linux-kernel
I guess :-) )

> iwl_mvm_sta->lock can be taken from BH, and therefore BH must be disabled if
> taking it from other contexts.
> 
> This fixes the lockdep warning below.

I don't think this is the right fix.

The only problem is this path:

>      SOFTIRQ-ON-W at:
>                        _raw_spin_lock+0x35/0x50
>                        iwl_mvm_tx_mpdu+0xae/0x5f0 [iwlmvm]
>                        iwl_mvm_tx_skb+0x200/0x470 [iwlmvm]
>                        iwl_mvm_mac_itxq_xmit+0xd5/0x1f0 [iwlmvm]
>                        iwl_mvm_add_new_dqa_stream_wk+0x34c/0x910 [iwlmvm]
>                        process_one_work+0x1f0/0x5b0

which I believe we just made use local_bh_disable() since there are
other reasons as well for that, IIRC.

Yes, here's the fix:

https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers.git/commit/?id=f5ae2f932e2f8f4f79796f44832ae8fca26f188a

It's on the way upstream.

Thanks for the patch/report though!

johannes