update mem info on every refresh on Solaris platform

[ViryBe]

The bug

htop crashes on illumos when the cpu count changes.

Tested with latest main branch on an illumos system. I unfortunately don't have a Solaris machine to test on it, but according to the man pages the bug should be the same.

How to reproduce:

1. Open htop in a terminal
2. Disable CPU0:

# as root
psradm -f 0
# to re-enable CPU0
psradm -Fn 0

htop crashed in first terminal.

Issue and Fix

The memory info was previously read only once and kept in a static variable. However, the pointer to the memory info is invalidated when the kstat chain is updated, such as when the cpu count changes.

From the Illumos kstat_chain_update man page:

[...] any kstat_t structures retrieved by the
kstat_lookup(3KSTAT) function or data pointers obtained through the
kstat_data_lookup(3KSTAT) function are invalidated by a call to
kstat_chain_update(). [...]

So, re-reading the struct kstat_t on every memory scan ensure that the pointer meminfo is always valid.

Note that I also replace the 2 calls to kstat_open and kstat_close by a single kstat_chain_update.

[natoscott]

@ViryBe thanks for looking into it.

I unfortunately don't have a Solaris machine to test on it

It'd be really good to test this no a Solaris machine before proceeding further - is there anyone out there who can help?

[ViryBe]

yeah, I'll try to install solaris in a VM to test the patch if I have some time in the following days

[BenBE]

Just a minor stylistic note, apart from that the change looks reasonable. Testing on Solaris might be nice.

[ViryBe]

Thanks for the feedback @BenBE.

I tested in a Solaris 11.4 VM and I can confirm that the bug is also present and the fix works as intended.