Re: [PATCH v5.7 8/8] iwlwifi: mvm: don't call iwl_mvm_free_inactive_queue() under RCU

From: Luca Coelho <luca@coelho.fi>
To: Mark Asselstine <asselsm@gmail.com>
Cc: kvalo@codeaurora.org,
	linux-wireless <linux-wireless@vger.kernel.org>,
	johannes.berg@intel.com
Subject: Re: [PATCH v5.7 8/8] iwlwifi: mvm: don't call iwl_mvm_free_inactive_queue() under RCU
Date: Fri, 17 Apr 2020 09:42:00 +0300	[thread overview]
Message-ID: <1c6acee636c0463c4c293ff910053f8b25b4da92.camel@coelho.fi> (raw)
In-Reply-To: <CAPuovE+_jWPjesRZ0GFk0zjf-jLmyyqOGxwyZGcawg5DL9CbXg@mail.gmail.com>

On Fri, 2020-04-03 at 10:28 -0400, Mark Asselstine wrote:
> I was looking into this as part of
> https://bugzilla.kernel.org/show_bug.cgi?id=206971 and had a similar
> fix in flight. My concern was that queue_owner being used outside of
> the RCU might be an issue as now you have no guaranty that the
> eventual use of sta->txq[tid] in iwl_mvm_free_inactive_queue() is
> going to be valid. The only way to work around this is instead of
> storing queue_owner, store mvmtxq = iwl_mvm_txq_from_tid(sta, i), then
> adjust iwl_mvm_free_inactive_queue(), iwl_mvm_disable_txq() and
> whatnot to take struct iwl_mvm_txq * instead of struct ieee80211_sta
> *. If you open the bug you will see the latest version of my work as
> the attached patch. I am not an RCU expert so I am curious to hear
> your thoughts.

I asked Johannes to check your comment.  For now, I'm going to drop it
from v2 of this patchset, so we can go ahead with the other patches.

--
Cheers,
Luca.