Re: [PATCH 1/9] iwlagn: need longer tx queue stuck timer for coex devices

["Guy, Wey-Yi" <wey-yi.w.guy@intel.com>]

Hi Stanislaw,

On Mon, 2010-10-18 at 05:12 -0700, Stanislaw Gruszka wrote:
> Hi Wey
> 
> > activity is too small time for device. Moreover we have unlikely but
> > possible situation when device is fully functional, but read_ptr will
> > wrap by accident to q->last_read_ptr on every check.
> > 
> > I think, better solution would be something like in rt2x00 or in
> > net/sched/sch_generic.c (however rt2x00 is easier to understand). It is
> > based on time stamp. When we get tx complete notification from hardware
> > (and incise read_ptr) mark the time stamp. In watchdog, which tick
> > periodically, check if queue is not empty and if current time is
> > bigger than time_stamp + time_out, if it is - firmware hung. More
> > smaller watchog tick give more precise hung detect (with disadvantage
> > of more cpu usage).
> > 
> > 
> > Me too not really like the current "monitor" approach, some thought about the design you propose.
> > 
> > 1. "time_out" is something need to be define and has the similar problem like what we have today since different devices has different behavior. For example, in WiFi/BT combo case, the queue might not move for a while if BT traffic load is high
> 
> Sure.
> 
> However new watchdog could be more precise. Currently if hung will
> happen just after watchdog tick we are detecting it in time about 2
> ticks i.e. 10s, or when happen just before the tick we detect the hang
> in 1 tick i.e. 5s, what gives 100% inaccuracy. New design can be much
> more precise.
> 
> > 2. I don't really see much of "cpu usage" impact if we have a reasonable watchdog timer. But it is all relative.
> 
> Ohh, I was talking about cpu usage in new design I described.
> 
> > 
> > By saying that, I think using timestamp might give more cleaner design, but still has the similar issues.
> 
> Ok, if Intel have no plan to change the monitor recovery and have nothing
> against my watchdog approach, I'm going to cook some patches.

Pleas do so and please do let us review it. I am very happy having you
looking at the iwlwifi driver and give great improvement.

Thank you very much
Wey