Re: [kvm-unit-tests PATCH v4 07/13] s390x: Use interrupts in SCLP

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On 2019-01-03 14:13, Janosch Frank wrote:
> On 03.01.19 13:58, Thomas Huth wrote:
>> On 2019-01-03 11:08, Janosch Frank wrote:
>>> We need to properly implement interrupt handling for SCLP, because on
>>> z/VM and LPAR SCLP calls are not synchronous!
>>>
>>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> [...]
>>> +
>>>  static void sclp_read_scp_info(ReadInfo *ri, int length)
>>>  {
>>>  	unsigned int commands[] = { SCLP_CMDW_READ_SCP_INFO_FORCED,
>>>  				    SCLP_CMDW_READ_SCP_INFO };
>>> -	int i;
>>> +	int i, cc;
>>>  
>>>  	for (i = 0; i < ARRAY_SIZE(commands); i++) {
>>>  		memset(&ri->h, 0, sizeof(ri->h));
>>>  		ri->h.length = length;
>>>  
>>> -		if (sclp_service_call(commands[i], ri))
>>> +		sclp_mark_busy();
>>> +		cc = sclp_service_call(commands[i], ri);
>>> +		sclp_wait_busy();
>>
>> You already do the sclp_wait_busy() in sclp_service_call now, so I think
>> you don't need the sclp_wait_busy() here anymore?
> 
> Yeah, that has to go.
> 
>>
>> Also, what about moving the sclp_mark_busy() calls to the beginning of
>> sclp_service_call() instead?
> 
> Wouldn't that create a race on the data of __sccb and we could end with
> garbled scb commands?

Since there is a sclp_wait_busy in sclp_service_call already, you can be
sure that the previous command already finished, can't you?

 Thomas



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