Re: 4.4: INFO: rcu_sched self-detected stall on CPU

From: Steven Haigh
Date: Tue Mar 29 2016 - 14:04:40 EST

Greg, please see below - this is probably more for you...

On 03/29/2016 04:56 AM, Steven Haigh wrote:
> Interestingly enough, this just happened again - but on a different
> virtual machine. I'm starting to wonder if this may have something to do
> with the uptime of the machine - as the system that this seems to happen
> to is always different.
> Destroying it and monitoring it again has so far come up blank.
> I've thrown the latest lot of kernel messages here:

So I just did a bit of digging via the almighty Google.

I started hunting for these lines, as they happen just before the stall:
BUG: Bad rss-counter state mm:ffff88007b7db480 idx:2 val:-1
BUG: Bad rss-counter state mm:ffff880079c638c0 idx:0 val:-1
BUG: Bad rss-counter state mm:ffff880079c638c0 idx:2 val:-1

I stumbled across this post on the lkml:

The patch attached seems to reference the following change in
unmap_mapping_range in mm/memory.c:
> - struct zap_details details;
> + struct zap_details details = { };

When I browse the GIT tree for 4.4.6:

I see at line 2411:
struct zap_details details;

Is this something that has been missed being merged into the 4.4 tree?
I'll admit my kernel knowledge is not enough to understand what the code
actually does - but the similarities here seem uncanny.

Steven Haigh

Email: netwiz@xxxxxxxxx
Phone: (03) 9001 6090 - 0412 935 897

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