From: Greg KH <gregkh@linuxfoundation.org>
To: Pavel Skripkin <paskripkin@gmail.com>
Cc: Larry.Finger@lwfinger.net, phil@philpotter.co.uk,
straube.linux@gmail.com, linux-staging@lists.linux.dev,
linux-kernel@vger.kernel.org,
"Fabio M . De Francesco" <fmdefrancesco@gmail.com>
Subject: Re: [PATCH] staging: r8188eu: remove _rtw_mutex_{init,free}
Date: Sat, 4 Sep 2021 09:34:08 +0200 [thread overview]
Message-ID: <YTMhcMSqWCepQMMT@kroah.com> (raw)
In-Reply-To: <20210903193356.31927-1-paskripkin@gmail.com>
On Fri, Sep 03, 2021 at 10:33:56PM +0300, Pavel Skripkin wrote:
> While testing Fabio's patch I hit lockdep warning about possible
> deadlock:
>
> [ 252.063305] WARNING: possible recursive locking detected
> [ 252.063642] 5.14.0+ #9 Tainted: G C
> [ 252.063946] --------------------------------------------
> [ 252.064282] ip/335 is trying to acquire lock:
> [ 252.064560] ffff888009ebad28 (pmutex){+.+.}-{4:4}, at: usbctrl_vendorreq+0xc5/0x4a0 [r8188eu]
> [ 252.065168]
> [ 252.065168] but task is already holding lock:
> [ 252.065536] ffffffffc021b3b8 (pmutex){+.+.}-{4:4}, at: netdev_open+0x3a/0x5f [r8188eu]
> [ 252.066085]
> [ 252.066085] other info that might help us debug this:
> [ 252.066494] Possible unsafe locking scenario:
> [ 252.066494]
> [ 252.066866] CPU0
> [ 252.067025] ----
> [ 252.067184] lock(pmutex);
> [ 252.067367] lock(pmutex);
>
> There is one problem with this warning: there is no pmutex in this
> driver, *BUT* all mutexes are initialized via private _rtw_mutex_init
> API, which had struct mutex *pmutex argument.
>
> So, all mutexes in this driver had same name in lockdep map. Of course,
> lockdep will complain about any nested locking.
>
> Fix it by open-coding _rtw_mutex_{init,free} wrappers, because we do not
> need them at all.
>
> Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Fixes: 15865124feed ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
No need for "Fixes:" on this, as it's not a bug, it's just a badly
designed implementation.
thanks,
greg k-h
next prev parent reply other threads:[~2021-09-04 7:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-03 19:33 [PATCH] staging: r8188eu: remove _rtw_mutex_{init,free} Pavel Skripkin
2021-09-04 7:34 ` Greg KH [this message]
2021-09-04 12:47 ` [PATCH v2] " Pavel Skripkin
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