netdev - Re: [PATCH v2] cfg80211: avoid holding the RTNL when calling the driver

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Date:   Mon, 25 Jan 2021 12:56:21 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Johannes Berg <johannes@...solutions.net>,
        linux-wireless@...r.kernel.org
Cc:     netdev@...r.kernel.org, Oliver Neukum <oneukum@...e.com>
Subject: Re: [PATCH v2] cfg80211: avoid holding the RTNL when calling the
 driver

Hi Johannes,

On 22.01.2021 13:27, Johannes Berg wrote:
>> This patch landed in today's (20210122) linux-next as commit
>> 791daf8fc49a ("cfg80211: avoid holding the RTNL when calling the
>> driver"). Sadly, it causes deadlock with mwifiex driver. I think that
>> lockdep report describes it enough:
> Yeah, umm, sorry about that. Evidently, I somehow managed to put
> "wiphy_lock()" into that part of the code, rather than "wiphy_unlock()"!
>
> I'll fix, thanks!

I've checked today's linux-next with the updated commit 27bc93583e35 
("cfg80211: avoid holding the RTNL when calling the driver") and there 
is still an issue there, but at least it doesn't cause a deadlock:

cfg80211: Loading compiled-in X.509 certificates for regulatory database
Bluetooth: vendor=0x2df, device=0x912a, class=255, fn=2
cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
Bluetooth: FW download over, size 533976 bytes
btmrvl_sdio mmc3:0001:2: sdio device tree data not available
mwifiex_sdio mmc3:0001:1: WLAN FW already running! Skip FW dnld
mwifiex_sdio mmc3:0001:1: WLAN FW is active
mwifiex_sdio mmc3:0001:1: CMD_RESP: cmd 0x242 error, result=0x2
mwifiex_sdio mmc3:0001:1: mwifiex_process_cmdresp: cmd 0x242 failed 
during       initialization
------------[ cut here ]------------
WARNING: CPU: 0 PID: 5 at net/wireless/core.c:1336 
cfg80211_register_netdevice+0xa4/0x198 [cfg80211]
Modules linked in: mwifiex_sdio mwifiex sha256_generic libsha256 
sha256_arm btmrvl_sdio btmrvl cfg80211 bluetooth s5p_mfc exynos_gsc 
v4l2_mem2mem videobuf2_dma_co
ntig videobuf2_memops videobuf2_v4l2 videobuf2_common videodev 
ecdh_generic ecc mc s5p_cec
CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 
5.11.0-rc4-00536-g27bc93583e35-dirty #2345
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: events request_firmware_work_func
[<c01116e8>] (unwind_backtrace) from [<c010cf58>] (show_stack+0x10/0x14)
[<c010cf58>] (show_stack) from [<c0b46744>] (dump_stack+0xa4/0xc4)
[<c0b46744>] (dump_stack) from [<c01270ac>] (__warn+0x118/0x11c)
[<c01270ac>] (__warn) from [<c0127164>] (warn_slowpath_fmt+0xb4/0xbc)
[<c0127164>] (warn_slowpath_fmt) from [<bf1a9de0>] 
(cfg80211_register_netdevice+0xa4/0x198 [cfg80211])
[<bf1a9de0>] (cfg80211_register_netdevice [cfg80211]) from [<bf28f2e4>] 
(mwifiex_add_virtual_intf+0x6a0/0x9f4 [mwifiex])
[<bf28f2e4>] (mwifiex_add_virtual_intf [mwifiex]) from [<bf26c79c>] 
(_mwifiex_fw_dpc+0x264/0x494 [mwifiex])
[<bf26c79c>] (_mwifiex_fw_dpc [mwifiex]) from [<c06c881c>] 
(request_firmware_work_func+0x58/0x94)
[<c06c881c>] (request_firmware_work_func) from [<c0149af8>] 
(process_one_work+0x30c/0x888)
[<c0149af8>] (process_one_work) from [<c014a0cc>] (worker_thread+0x58/0x594)
[<c014a0cc>] (worker_thread) from [<c015105c>] (kthread+0x154/0x19c)
[<c015105c>] (kthread) from [<c010011c>] (ret_from_fork+0x14/0x38)
Exception stack(0xc1cedfb0 to 0xc1cedff8)
...
---[ end trace c04a86d3eb55e7cb ]---
mwifiex_sdio mmc3:0001:1: info: MWIFIEX VERSION: mwifiex 1.0 (14.68.29.p59)
mwifiex_sdio mmc3:0001:1: driver_version = mwifiex 1.0 (14.68.29.p59)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland