Re: [PATCH] scsi: fix duplicate host number

[Joe Eykholt <jeykholt@cisco.com>]

Stefan Richter wrote:
> Joe Eykholt wrote:
>> Subtract 1, so that scsi_host still starts with 0.
> ...
>> -static int scsi_host_next_hn;        /* host_no for next new host */
>> +static atomic_t scsi_host_next_hn;    /* host_no for next new host */
>>  
>>  
>>  static void scsi_host_cls_release(struct device *dev)
>> @@ -333,7 +333,7 @@ struct Scsi_Host *scsi_host_alloc(struct 
>> scsi_host_template *sht, int privsize)
>>  
>>      mutex_init(&shost->scan_mutex);
>>  
>> -    shost->host_no = scsi_host_next_hn++; /* XXX(hch): still racy */
>> +    shost->host_no = atomic_inc_return(&scsi_host_next_hn) - 1;
> 
> Can also be written
> 
> static atomic_t scsi_host_next_hn = ATOMIC_INIT(-1);
> ...
>     shost->host_no = atomic_inc_return(&scsi_host_next_hn);

Yes, I considered that, but then the variable name and comment wouldn't be correct.

Also, the initializer adds 4 bytes to the initialized data section, and
the code for -1 should increase text size by less than that, so I think it's a wash.
An atomic_fetch_and_add() would be handy.

	Cheers,
	Joe