[ath9k-devel] [PATCH 1/3] mac80211: move mesh sync beacon handler into neighbour_update

[Johannes Berg <johannes@sipsolutions.net>]

On Mon, 2013-02-18 at 16:07 +0100, Marco Porsch wrote:

> > I guess you can tell I'm not in a good mood today. I think any use of
> > get_tsf() for operation is a complete waste of time, there's no way you
> > can get the timings correct. You could be preempted, and suddenly sleep
> > for a few tens or hundreds milliseconds, so none of this makes any
> > sense... To properly do it you have to do calculations in relative times
> > and let the device apply them.
> 
> I don't get your last sentence here. Maybe you can elaborate?

I'm saying what could happens is this:

 tsf = drv_get_tsf()
 [be preempted, 100ms later]
 do_something_with(tsf)

so I think using drv_get_tsf() is pretty much always wrong.


> Concerning timestamp vs. TSF usage; wow - I tested it when using the 
> timestamp value for TBTT scheduling. Works fine. Works even better than 
> TSF as it slightly reduces the measured wakeup overhead.
> 
> Hm, I was sure the TSF as in *now* would be more appropriate than the 
> TSF at receipt time... But either way, if it works better and is less 
> ugly, it is a win-win =)
> 
> I'll send an updated patch with the more intuitive API.

:)

johannes