Genode on RPI - second round

[Stefan Kalkowski]

Hi Tomasz,

first of all: congratulation for going that far with RPI3.

On Mon, Feb 18, 2019 at 11:21:10PM +0100, Tomasz Gajewski wrote:
> 
> Hi again,
> 
> > 3. run/smp test hangs during threads destruction
> >
> > Like I wrote earlier run/smp test is almost working on multiple
> > cores. It hangs somewhere in [5] during destructing thread running
> > non-zero core (destroying first one does not cause problems).
> >
> > I don't have any concrete questions here. The only ones are:
> >
> >  a. Does this test properly work on arndale?
> >
> >  b. Do you have any thoughts what can go wrong? Maybe I haven't
> >     implemented something important for smp yet? Only timer and IPI?
> 
> Situation with this test has changed after I rebased my branch to
> current staging. It doesn't stop at threads destruction in Affinity test
> like earlier so probably something was fixed since 18.11 release.
> 
> Currently it hangs a little further:
> 
> ...
> init -> test-smp] Affinity: Round 09:  A  A  A  A 
> [init -> test-smp] Affinity:     CPU: 00 01 02 03 
> [init -> test-smp] Affinity: Round 10:  A  A  A  A 
> [init -> test-smp] Affinity: --- test finished ---
> [init -> test-smp] TLB: --- test started ---
> [init -> test-smp] TLB: thread started on CPU 1
> [init -> test-smp] TLB: thread started on CPU 2
> [init -> test-smp] TLB: thread started on CPU 3
> [init -> test-smp] TLB: all threads are up and running...
> [init -> test-smp] TLB: ram dataspace destroyed, all will fault...
> no RM attachment (READ pf_addr=0xc00c pf_ip=0x1000d2c from pager_object: pd='init -> test-smp' thread='tlb_thread') 
> Warning: page fault, pager_object: pd='init -> test-smp' thread='tlb_thread' ip=0x1000d2c fault-addr=0xc00c type=no-page
> Warning: core -> pager_ep: cannot submit unknown signal context
> [init -> test-sm
> 

The page-fault of this tlb-thread is perfectly fine! It is what is
tested here exactly. Actually, you should see three faulting
tlb-threads.
The test forks threads on each cpu apart from the first one, and let
them infinetly work on a shared page, which is thereby in the TLB of
the corresponding cpu. Because we do not start anything else on the
other cpus, there is little probability that the TLB entry gets
evicted. Then the first cpu unmaps the page. If cross-cpu TLB
shootdown is implemented correctly for the platform, you should notice
a fault on all other cpus.

The question is why your messages end here, or did you just send a
snippet?

Regards
Stefan

> Can you say if this reported fault is something that currently happens
> on tested configurations on staging or is it specific to my rpi work?
> 
> I can investigate it, but if it's something generic it will be much
> harder for me than for you and probably you will get it working quicker.
> 
> Tomasz Gajewski
> 
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-- 
Stefan Kalkowski
Genode labs

https://github.com.skalk | https://genode.org