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

From: "Kevin P. Fleming" <kpfleming@cox.net>
To: Greg KH <greg@kroah.com>
Cc: Oliver Neukum <oliver@neukum.org>, Robert Love <rml@tech9.net>,
	Patrick Mochel <mochel@osdl.org>, Andrew Morton <akpm@digeo.com>,
	sdake@mvista.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] udev enhancements to use kernel event queue
Date: Wed, 18 Jun 2003 17:12:50 -0700	[thread overview]
Message-ID: <3EF10002.7020308@cox.net> (raw)
In-Reply-To: <20030618225913.GB2413@kroah.com>

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 :-)