Re: odd panic

[Andrew Doran <ad%netbsd.org@localhost>]

Hi Michael,

On Thu, Dec 26, 2019 at 11:04:12AM -0800, Michael Cheponis wrote:

> what does this mean?  (Received last night on RPi 3B+ that has been h/w
> stable):
> 
> panic: kernel diagnostic assertion "uvmexp.swpgonly + npages <=
> uvmexp.swpginuse" failed: file "/c/usr/src/sys/uvm/uvm_pager.c", line 472
> 
> load averages:  3.32,  3.72,  3.93;               up 0+11:45:09
>  09:54:27    UTC
> 63 processes: 6 runnable, 53 sleeping, 4 on CPU
> CPU0 states: 68.6% user,  0.0% nice, 27.6% system,  3.8% interrupt,  0.0%
> idle
> CPU1 states: 94.3% user,  0.0% nice,  5.7% system,  0.0% interrupt,  0.0%
> idle
> CPU2 states: 89.5% user,  0.0% nice, 10.5% system,  0.0% interrupt,  0.0%
> idle
> CPU3 states: 74.0% user,  0.0% nice, 17.3% system,  8.7% interrupt,  0.0%
> idle
> Memory: 403M Act, 204M Inact, 13M Wired, 31M Exec, 259M File, 15M Free
> Swap: 3425M Total, 7912K Used, 3418M Free
> 
> [   1.0000000] NetBSD 9.99.17 (GENERIC) #2: Wed Nov 13 09:59:13 UTC 2019
> [   1.0000000]  mac%S.Culver.Net@localhost:
> /c/usr/src/sys/arch/evbarm/compile/obj/GENERIC
> 
> after reboot:
> 
> # swapctl -l
> Device      1K-blocks     Used    Avail Capacity  Priority
> /dev/ld0b      131072        0   131072     0%    1
> /swapfile     3376384        0  3376384     0%    2
> Total         3507456        0  3507456     0
> 
> So it seems like there was plenty of Swap available.

I just removed this assertion with rev 1.118 of src/sys/uvm/uvm_pager.c.
The assertion itself is not safe and can race on a multi-CPU machine.

Andrew