Message-ID: <e1e6a44581a711750d205f5d7f1ee68faf3e07aa.camel@sipsolutions.net>
Subject: Re: iwlwifi suspicous RCU usage warnings with kernel 5.15 and
 5.16-rc3
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Chris Murphy <lists@colorremedies.com>,
        Hans de Goede <hdegoede@redhat.com>
Cc:     Luca Coelho <luciano.coelho@intel.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless <linux-wireless@vger.kernel.org>
Date:   Tue, 30 Nov 2021 13:16:32 +0100
In-Reply-To: <CAJCQCtStsk8_a+p819g4WJf0hJAokJiMeEeouaMpw8ar5_PH8g@mail.gmail.com>
References: <348f1b9c-f1b4-8a01-873f-9749f1070808@redhat.com>
         <CAJCQCtStsk8_a+p819g4WJf0hJAokJiMeEeouaMpw8ar5_PH8g@mail.gmail.com>
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On Mon, 2021-11-29 at 15:12 -0500, Chris Murphy wrote:
> On Mon, Nov 29, 2021 at 7:39 AM Hans de Goede <hdegoede@redhat.com> wrote:
> > 
> > Hi All,
> > 
> > Since kernel 5.15 (IIRC) I've been getting a suspicous RCU usage warning
> > from the iwlwifi driver when running a kernel with checks for this enabled.
> > 
> > Note this is the 2nd or 3th time this happens now, can we please get
> > some CI checks for these (assuming there is some iwlwifi CI already) ?
> 
> I mentioned it back in October ...
> https://lore.kernel.org/linux-wireless/CAJCQCtR28JZaqNC053jEpoZGN37kRK9ReYX0Kt8+ukRGnO5z_Q@mail.gmail.com/
> 
> And it's still happening with 5.16-rc3 out today.
> 

We have this code:

static int iwl_mvm_start_get_nvm(struct iwl_mvm *mvm)
{
        int ret;

        rtnl_lock();
        mutex_lock(&mvm->mutex);


but internally we already have

static int iwl_mvm_start_get_nvm(struct iwl_mvm *mvm)
{
...
        rtnl_lock();
        wiphy_lock(mvm->hw->wiphy);
        mutex_lock(&mvm->mutex);


so that's surely the issue - Luca, do you already have any patches for
this out? It was internally through a merge, so no explicit change, and
I guess upstream I forgot when doing the RTNL work?

johannes