bin/59996: swapctl: SWAP_STATS different to SWAP_NSWAP (1 != 3)

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>Number:         59996
>Category:       bin
>Synopsis:       swapctl: SWAP_STATS different to SWAP_NSWAP (1 != 3)
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 11 23:05:00 +0000 2026
>Originator:     Thomas Klausner
>Release:        NetBSD 11.99.5
>Organization:
	
>Environment:
	
	
Architecture: x86_64
Machine: amd64
>Description:
When running "swapctl -l" in a loop (1/s) on a busy machine (bulk build)
with 10%-25% of available swap used, I sometimes see errors like

swapctl: SWAP_STATS different to SWAP_NSWAP (1 != 3)

I changed the code to use warn() instead of warnx(), but errno is not set:

swapctl: SWAP_STATS different to SWAP_NSWAP (2 != 3): Undefined error: 0
swapctl: SWAP_STATS different to SWAP_NSWAP (1 != 3): Undefined error: 0
swapctl: SWAP_STATS different to SWAP_NSWAP (1 != 3): Undefined error: 0

The machine does have three swap devices, so '3' is the correct value.
>How-To-Repeat:
Run a bulk build.  (Doesn't work on an unloaded machine, I think.)

In a second window, run:
while true; do sleep 1; swapctl -l; done

Wait. Be lucky.


>Fix:
Please.

>Unformatted: