Re: BUG: unable to handle kernel paging request from pty_write [was: Linux 4.4.2]

From: Steven Rostedt
Date: Thu Feb 25 2016 - 14:23:46 EST

On Thu, 25 Feb 2016 11:09:35 -0800
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> Jiri, were you messing around with tracing when this happened? Or
> maybe shutting down CPU's? There was a RCU locking problem with CPU
> shutdown, maybe this is one of the symptoms. The fix for that is
> recent, and not in 4.4.2.
> Adding Steven Rostedt to the cc. Steven, does that look like a possible case?

Possible: yes. Likely: no

The recent fix would require shutting down a CPU at the same time as a
tracepoint is enabled or disabled. Rather difficult to hit, but easier
on a virtual machine. If Jiri was not enabling/disabling tracepoints or
shutting down CPUs, then it would not be the bug.

But as the comm of the bug is gdb and this running on a virtual
machine, I think the bug may be elsewhere. Corrupt stack possibly?

-- Steve