get_swap_page hanged when turning the computer off

R

rihad

Sometimes this happens. A workaround is to call swapoff manually before rebooting. But the question is, why is it that some computers (or FreeBSD versions?) freeze forever with that message on the screen and require manual intervention to reboot, while some others do that automatically?
 
A: More details would be welcome, actually necessary to help debug this problem. What version, rough hardware configuration, what exactly happens, what are the exact messages?
B: If my interpolation of what you mean is correct (big if, see item A above), then this is a kernel bug. In that case, you should raise it on the developer mailing list, or open a bug report (a.k.a. PR), or if a PR already exists, add information to it.
 
The problem is easily repeatable. For example create a VMware or similar VPS, running any recent or not so recent version of FreeBSD, and make sure it uses some swap - mere 5-10 mb swap in use are often enough.
Bourne shell example:
Bash: 
$ mem="$(dd if=/dev/zero bs=1m count=500)"
$ sudo reboot
But VMware reboots fine after kernel panic. Some other real PCs do too. Some do not. The question isn't really about why the panic occurs in the first place, but why some computers choose not to complete the reboot after that. Or maybe it's configurable somewhere?
 
Actually seeing this problem on real hardware is what motivated me to open this thread. Just saying that I've also been seeing this swap panic upon reboot/halt on VMware for the past several years. With or without zfs.
 
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