Re: [PATCH] udev enhancements to use kernel event queue

[Kevin P. Fleming]

Greg KH wrote:

>>If this kmalloc fails, you'll have a hole in the numbers and
>>user space will be very confused. You need to report dropped
>>events if you do this.
> 
> 
> Yes, we should add the sequence number last.
> 

While this is not a bad idea, I don't think you want to make a promise 
to userspace that there will never be gaps in the sequence numbers. When 
this sequence number was proposed, in my mind it seemed perfect because 
then userspace could _order_ multiple events for the same device to 
ensure they got processed in the correct order. I don't know that any 
hotplug userspace implementation is going to be large and complex enough 
to warrant "holding" events until lower-numbered events have been 
delivered. That just seems like a very difficult task with little 
potential gain, but I could very well be mistaken :-)