I'm still tryin to understand why all my servers seem to be ok even if they have kernel that should be affected and some of them are running mysql... For example one of them is a debian kernel 2.6.32 running mysql and ntpd, and i see in dmesg Clock: inserting leap second 23:59:60 UTC but the cpu load is ok...
The leap second was scheduled in January. That event is so unusual you might get worried. So you do a simple google search and find out that there was a critical bug in Linux kernel last time leap second was inserted. People got worried rightfully. I don't know about debian, if it was known prior, if it is the same bug as before, ... But I don't run Debian, you do.
Don't get me wrong, I wouldn't too by default. But do you remember Azure crashing on February 29th? And checking for that date is a matter of three conditions. Leap second is much more complex. I'm not trying to be a smart-ass.. I'm just saying it's something I would worry about and would try to find something about it. And perhaps it wouldn't lead anywhere with Debian.
And still, something in your app stack could crash on this as well, leaving the kernel patching pointless.