netdev - Re: [PATCH v3 2/2] net/ibmvnic: prevent more than one thread from running in reset

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Message-ID: <87ef0ew2so.fsf@mpe.ellerman.id.au>
Date:   Wed, 18 Sep 2019 16:12:39 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Juliet Kim <julietk@...ux.vnet.ibm.com>, netdev@...r.kernel.org
Cc:     julietk@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org,
        tlfalcon@...ux.vnet.ibm.com
Subject: Re: [PATCH v3 2/2] net/ibmvnic: prevent more than one thread from running in reset

Hi Juliet,

Juliet Kim <julietk@...ux.vnet.ibm.com> writes:
> Signed-off-by: Juliet Kim <julietk@...ux.vnet.ibm.com>
> ---
>  drivers/net/ethernet/ibm/ibmvnic.c | 23 ++++++++++++++++++++++-
>  drivers/net/ethernet/ibm/ibmvnic.h |  3 +++
>  2 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index ba340aaff1b3..f344ccd68ad9 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -2054,6 +2054,13 @@ static void __ibmvnic_reset(struct work_struct *work)
>  
>  	adapter = container_of(work, struct ibmvnic_adapter, ibmvnic_reset);
>  
> +	if (adapter->resetting) {
> +		schedule_delayed_work(&adapter->ibmvnic_delayed_reset,
> +				      IBMVNIC_RESET_DELAY);
> +		return;
> +	}
> +
> +	adapter->resetting = true;
>  	reset_state = adapter->state;

Is there some locking/serialisation around this?

Otherwise that looks very racy. ie. two CPUs could both see
adapter->resetting == false, then both set it to true, and then continue
executing and stomp on each other.

cheers