netdev - Re: [PATCH] rhashtable: use irq-safe spinlock in rhashtable_rehash

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Message-ID: <726dba28e925c6ade53f362c4f48b2ee28841dc2.camel@sipsolutions.net>
Date:   Wed, 06 Feb 2019 09:15:15 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     Jouni Malinen <j@...fi>, Thomas Graf <tgraf@...g.ch>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH] rhashtable: use irq-safe spinlock in
 rhashtable_rehash_table()

On Tue, 2019-02-05 at 15:37 +0100, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
> 
> When an rhashtabl walk is done from irq/bh context, we rightfully
> get a lockdep complaint saying that we could get a (soft-)IRQ in
> the middle of a rehash. This happened e.g. in mac80211 as it does
> a walk in soft-irq context.
> 
> Fix this by using irq-safe locking here. We don't need _irqsave()
> as we know this will be called only in process context from the
> workqueue. We could get away with _bh() but that seems a bit less
> generic, though I'm not sure anyone would want to do a walk from
> a real IRQ handler.

Please drop this, it doesn't make sense.

I'll resend with all the spinlock usage changed to either _bh or
_irqsave(), since it makes no sense to enforce any kind of outside
BH/irq disabling for purposes of the inner lock.

johannes