Am 27.11.2016 um 09:13 schrieb H. Nikolaus Schaller hns@goldelico.com:
Am 27.11.2016 um 02:59 schrieb Michael Mrozek EvilDragon@openpandora.org:
Am Sat, 26 Nov 2016 23:25:03 +0100 hat "H. Nikolaus Schaller" hns@goldelico.com geschrieben:
Hi,
it means that something is consuming all your CPU power - which is probably the NEON loop ;)
http://unix.stackexchange.com/questions/252045/rcu-preempt-detected-stalls-o...
Yes, this would mean that the NEON pipeline stops processing, i.e. is no longer advancing to the next assembler instruction.
But why does it occur only with this voltage level? And how can it happen at all?
I think I have an answer what happens.
There are two A15 cores. And due to slightly different parameters one of the core continues to work while for the other some transistors are too slow for the given frequency and voltage level (they are faster for higher voltage) and some flip-flops stop switching when they should.
This mangles up instruction processing and the second core recognises that the other one is not completing some rcu task (by setting some semaphore bit).
And the LEDs threads and the controlling bash command (crl-C) are frozen as well because these are scheduled to run on the frozen A15 core.
So it is just a very peculiar symptom of a low-voltage/high-frequency partial freeze.
What does this "INFO: rcu_preempt self-detected stall on CPU" mean? Does this give a hint what is going wrong? Is something wrong in some SoC interconnect? Or is just one core recognising that the other core did freeze?
BR and thanks, Nikolaus
Kernel mailing list Kernel@pyra-handheld.com http://pyra-handheld.com/cgi-bin/mailman/listinfo/kernel
-- Mit freundlichen Grüßen,
Michael Mrozek
OpenPandora GmbH Geschäftsführer: Michael Mrozek
Schäffbräustr. 11 85049 Ingolstadt Deutschland Tel.: 0841 / 990 5548 http://www.openpandora.de/ HRB 4879, Amtsgericht Ingolstadt
eMail: mrozek@openpandora.org
Kernel mailing list Kernel@pyra-handheld.com http://pyra-handheld.com/cgi-bin/mailman/listinfo/kernel