From: Johannes Berg <johannes@sipsolutions.net>
To: Ben Greear <greearb@candelatech.com>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Re: lockdep warning in mac80211/tx.c, 4.13.16+ kernel, ath9k related
Date: Thu, 01 Feb 2018 23:40:37 +0100 [thread overview]
Message-ID: <1517524837.28814.14.camel@sipsolutions.net> (raw)
In-Reply-To: <e8f8b910-ffa8-fbc7-3152-58ccf70b1ace@candelatech.com>
On Thu, 2018-02-01 at 14:33 -0800, Ben Greear wrote:
>
> All of RCU is suspicious
Heh.
The code does a plain rcu_dereference(), no locking other than
rcu_read_lock() involved.
On second thought though, I'm not convinced that your modifications
caused the problem.
Given your call stack, we'd expect rcu_read_lock() somewhere around
ath_tid_dequeue (or its caller(s)), since ieee80211_tx_dequeue clearly
requires it.
Normally, ieee80211_tx_dequeue() is called from various places that
probably come from mac80211 and already hold the rcu_read_lock(), e.g.
the wake_tx_queue op.
In this case, you're coming from drv_sta_state, so not sure why the
driver thinks it's OK to call the dequeue there.
johannes
next prev parent reply other threads:[~2018-02-01 22:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-01 0:53 lockdep warning in mac80211/tx.c, 4.13.16+ kernel, ath9k related Ben Greear
2018-02-01 22:23 ` Johannes Berg
2018-02-01 22:33 ` Ben Greear
2018-02-01 22:40 ` Johannes Berg [this message]
2018-02-01 22:47 ` Johannes Berg
2018-02-01 23:21 ` Ben Greear
2018-02-02 10:19 ` Toke Høiland-Jørgensen
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