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Sender: Larry Finger <larry.finger@gmail.com>
Message-ID: <33aff1cc-37f9-88a5-9fd5-5d8db21dc42d@lwfinger.net>
Date:   Mon, 8 May 2023 13:58:28 -0500
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Subject: Re: [PATCH] wifi: rtw88: use work to update rate to avoid RCU warning
Content-Language: en-US
To:     Ping-Ke Shih <pkshih@realtek.com>, kvalo@kernel.org,
        tony0620emma@gmail.com
Cc:     stable@vger.kernel.org, linux-wireless@vger.kernel.org
References: <20230508085429.46653-1-pkshih@realtek.com>
From:   Larry Finger <Larry.Finger@lwfinger.net>
In-Reply-To: <20230508085429.46653-1-pkshih@realtek.com>
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On 5/8/23 03:54, Ping-Ke Shih wrote:
> The ieee80211_ops::sta_rc_update must be atomic, because
> ieee80211_chan_bw_change() holds rcu_read lock while calling
> drv_sta_rc_update(), so create a work to do original things.
> 
>   Voluntary context switch within RCU read-side critical section!
>   WARNING: CPU: 0 PID: 4621 at kernel/rcu/tree_plugin.h:318
>   rcu_note_context_switch+0x571/0x5d0
>   CPU: 0 PID: 4621 Comm: kworker/u16:2 Tainted: G        W  OE
>   Workqueue: phy3 ieee80211_chswitch_work [mac80211]
>   RIP: 0010:rcu_note_context_switch+0x571/0x5d0
>   Call Trace:
>    <TASK>
>    __schedule+0xb0/0x1460
>    ? __mod_timer+0x116/0x360
>    schedule+0x5a/0xc0
>    schedule_timeout+0x87/0x150
>    ? trace_raw_output_tick_stop+0x60/0x60
>    wait_for_completion_timeout+0x7b/0x140
>    usb_start_wait_urb+0x82/0x160 [usbcore
>    usb_control_msg+0xe3/0x140 [usbcore
>    rtw_usb_read+0x88/0xe0 [rtw_usb
>    rtw_usb_read8+0xf/0x10 [rtw_usb
>    rtw_fw_send_h2c_command+0xa0/0x170 [rtw_core
>    rtw_fw_send_ra_info+0xc9/0xf0 [rtw_core
>    drv_sta_rc_update+0x7c/0x160 [mac80211
>    ieee80211_chan_bw_change+0xfb/0x110 [mac80211
>    ieee80211_change_chanctx+0x38/0x130 [mac80211
>    ieee80211_vif_use_reserved_switch+0x34e/0x900 [mac80211
>    ieee80211_link_use_reserved_context+0x88/0xe0 [mac80211
>    ieee80211_chswitch_work+0x95/0x170 [mac80211
>    process_one_work+0x201/0x410
>    worker_thread+0x4a/0x3b0
>    ? process_one_work+0x410/0x410
>    kthread+0xe1/0x110
>    ? kthread_complete_and_exit+0x20/0x20
>    ret_from_fork+0x1f/0x30
>    </TASK>
> 
> Cc: stable@vger.kernel.org
> Fixes: c1edc86472fc ("rtw88: add ieee80211:sta_rc_update ops")
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Link: https://lore.kernel.org/linux-wireless/f1e31e8e-f84e-3791-50fb-663a83c5c6e9@lwfinger.net/T/#t
> Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
> ---
>   drivers/net/wireless/realtek/rtw88/mac80211.c |  2 +-
>   drivers/net/wireless/realtek/rtw88/main.c     | 15 +++++++++++++++
>   drivers/net/wireless/realtek/rtw88/main.h     |  3 +++
>   3 files changed, 19 insertions(+), 1 deletion(-)

Tested-by: Larry Finger <Larry.Finger@lwfinger.net>

Thanks,

Larry