netdev - Re: [PATCH net-next 3/3] iavf: fix locking of critical sections

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Date:   Tue, 20 Jul 2021 13:31:53 +0200
From:   Jakub Kicinski <kuba@...nel.org>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>
Cc:     davem@...emloft.net, Stefan Assmann <sassmann@...nic.de>,
        netdev@...r.kernel.org,
        Konrad Jankowski <konrad0.jankowski@...el.com>
Subject: Re: [PATCH net-next 3/3] iavf: fix locking of critical sections

On Mon, 19 Jul 2021 09:31:54 -0700, Tony Nguyen wrote:
> To avoid races between iavf_init_task(), iavf_reset_task(),
> iavf_watchdog_task(), iavf_adminq_task() as well as the shutdown and
> remove functions more locking is required.
> The current protection by __IAVF_IN_CRITICAL_TASK is needed in
> additional places.
> 
> - The reset task performs state transitions, therefore needs locking.
> - The adminq task acts on replies from the PF in
>   iavf_virtchnl_completion() which may alter the states.
> - The init task is not only run during probe but also if a VF gets stuck
>   to reinitialize it.
> - The shutdown function performs a state transition.
> - The remove function performs a state transition and also free's
>   resources.
> 
> iavf_lock_timeout() is introduced to avoid waiting infinitely
> and cause a deadlock. Rather unlock and print a warning.

I have a vague recollection of complaining about something like this
previously. Why not use a normal lock? Please at the very least include
an explanation in the commit message.

If you use bit locks you should use the _lock and _unlock flavours of
the bitops.