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

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Date:   Wed, 18 Sep 2019 17:21:24 -0500
From:   Juliet Kim <julietk@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>, netdev@...r.kernel.org
Cc:     tlfalcon@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 2/2] net/ibmvnic: prevent more than one thread from
 running in reset


On 9/18/19 1:12 AM, Michael Ellerman wrote:
> 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

I agree there may be a race here. Thank you for reviewing.

I will address it in the next version.