Re: [PATCH] osm_sm_state_mgr.c: Fix handling of polling retry number

[Line Holen <line.holen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On 12/03/13 14:17, Hal Rosenstock wrote:
> On 11/27/2013 9:42 AM, Line Holen wrote:
>> On 11/27/13 13:16, Hal Rosenstock wrote:
>>> On 11/15/2013 7:15 AM, Line Holen wrote:
>>>> The retry counter is now only updated if a packet is actually sent.
>>>> (But as before the initial request is also counted.)
>>>>
>>>> Prior to this change the actual maximum number of packets sent were
>>>> polling retry number minus one.
>>>>
>>>> Signed-off-by: Line Holen<line.holen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
>>>>
>>>> ---
>>>>
>>>> diff --git a/opensm/osm_sm_state_mgr.c b/opensm/osm_sm_state_mgr.c
>>>> index 596ad8f..6eff9ee 100644
>>>> --- a/opensm/osm_sm_state_mgr.c
>>>> +++ b/opensm/osm_sm_state_mgr.c
>>>> @@ -197,16 +197,14 @@ void osm_sm_state_mgr_polling_callback(IN void
>>>> *context)
>>>>        }
>>>>
>>>>        /*
>>>> -     * Incr the retry number.
>>>> -     * If it reached the max_retry_number in the subnet opt - call
>>>> +     * If retry number reached the max_retry_number in the subnet
>>>> opt - call
>>>>         * osm_sm_state_mgr_process with signal
>>>> OSM_SM_SIGNAL_POLLING_TIMEOUT
>>>>         */
>>>> -    sm->retry_number++;
>>>>        OSM_LOG(sm->p_log, OSM_LOG_VERBOSE, "SM State %d (%s), Retry
>>>> number:%d\n",
>>>>            sm->p_subn->sm_state,
>>>> osm_get_sm_mgr_state_str(sm->p_subn->sm_state),
>>>>            sm->retry_number);
>>>>
>>>> -    if (sm->retry_number>= sm->p_subn->opt.polling_retry_number) {
>>>> +    if (sm->retry_number>   sm->p_subn->opt.polling_retry_number) {
>>>>            OSM_LOG(sm->p_log, OSM_LOG_DEBUG,
>>>>                "Reached polling_retry_number value in retry_number. "
>>>>                "Go to DISCOVERY state\n");
>>>> @@ -214,6 +212,9 @@ void osm_sm_state_mgr_polling_callback(IN void
>>>> *context)
>>>>            goto Exit;
>>>>        }
>>>>
>>>> +    /* Increment the retry number */
>>>> +    sm->retry_number++;
>>> Would it be better to increment retry number if
>>> sm_state_mgr_send_master_sm_info_req call just below this succeeds ?
>>>
>>> -- Hal
>> I'm not sure really.
> All I was proposing was a minor variation to what you proposed:
> to add a status return to sm_state_mgr_send_master_sm_info_req and only
> increment the retry_number if that call was "successful".
Understood.
>
>> The current placement was to avoid potential race
>> with response handling
>> and the clearing of the counter there (incrementing after the response
>> were received).
> Maybe I'm missing something but I don't see how this changes any
> potential race condition other than perhaps a smaller time window.
With the current locking and moving the increment later you could end up 
processing
the response (and clear the counter) and then increment it afterwords in 
this function.
With the suggested patch you'd increment every time you would attempt to 
send a
packet. Not perfect, but at least better than it used to be and it did 
not introduce any race.
>
>> Seemed to me that this could happen with the current locking.
> Yes, it looks to me like the locking here needs fixing. I'll send a
> patch for this shortly...
OK, good. Do you want me to send a v2 rebased on top of this patch that 
incorporate
your initial comment ?

Line

>
> -- Hal
>
>> Line
>>>> +
>>>>        /* Send a SubnGet(SMInfo) request to the remote sm (depends on
>>>> our state) */
>>>>        sm_state_mgr_send_master_sm_info_req(sm);
>>>>
>>>> -- 
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>>

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