linux-kernel - Re: [PATCH v5.1-rc] iwlwifi: make locking in iwl_mvm_tx

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Message-ID: <01d55c5cf513554d9cbdee0b14f9360a8df859c8.camel@sipsolutions.net>
Date:   Mon, 15 Apr 2019 13:37:30 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5.1-rc] iwlwifi: make locking in iwl_mvm_tx_mpdu()
 BH-safe

On Mon, 2019-04-15 at 13:33 +0200, Jiri Kosina wrote:

> > Yes, here's the fix:
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers.git/commit/?id=f5ae2f932e2f8f4f79796f44832ae8fca26f188a
> > 
> > It's on the way upstream.
> 
> If there are other reasons why disable BH for the whole function (are 
> there?), then this bigger hammer works as well of course.

I thought there are, but seeing the commit log here I'm not sure.

In any case, even if not, the function itself is part of the TX fast
path, but the caller from the workqueue is very uncommon (basically only
happens for a handful of packets on each new RA/TID), so I'd say that'd
be a good reason to use the slightly bigger hammer (it's not that much
different really, if you look at how much code is covered by the lock)
and avoid doing it all the time when we know it to be not needed.

> 	Tested-by: Jiri Kosina <jkosina@...e.cz>

Too late now to add this to the git tree, but thanks for checking! :-)

johannes