Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler

["Remy Bohmer" <linux@bohmer.net>]

Hello Haavard,

> That's what I was thinking too. If this is indeed the cause, the
> dev_err() added by the debug patch I posted should trigger and we may
> consider boosting the priority of the tasklet (using
> tasklet_hi_schedule.)

Notice that we are talking about Preempt-RT here. Everything is
running in thread context, even tasklets, softirqs etc. They are _all_
preemptible, and if Michael has some RT-thread in the system that has
a higher priority than this tasklet or softirq, than the buffer will
eventually overflow.
I wonder also if Michael has set the RT-priorities correctly, on RT
_every_ softirq/irq thread starts by default on priority 50,
SCHED_FIFO. If they are still at 50, any other softirq/tasklet, or irq
can make this behavior worse.
Notice that the default 50 thingy rarely gives a decent behaving
system. (But any other default will also give problems anyway, so it
_has_ to be customized/tuned by the end user)

Kind Regards,

Remy