Re: recurring tstile hangs on -current

[Thomas Klausner <tk%giga.or.at@localhost>]

On Mon, Jul 01, 2019 at 07:02:06AM -0000, Michael van Elst wrote:
> tk%giga.or.at@localhost (Thomas Klausner) writes:
> 
> >So it looks like it could be a very extreme slowness instead of a
> >complete deadlock.
> 
> When it stops, try to reduce kern.maxvnodes to something low (like 100),
> you can restore it, if the machine wakes up.
> 
> If this is a memory shortage instead of a deadlock, this will easily
> free kernel memory. You may need to wait 1-2 minutes to let the
> page daemon collect free pages.
> 
> If you cannot issue a sysctl command, you can patch the kernel variable
> "desiredvnodes" with DDB instead.

From some debugging so far, the cause for the hang seems to be that
the nvme driver is waiting for an interrupt that doesn't come.

At least once I got it to get unstuck by call "nvme_intr()" on the
softc address from ddb.
 Thomas