Re: kern/51412: Syscall I/O race condition leads to deadlock and lost interrupts

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/51412; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/51412: Syscall I/O race condition leads to deadlock and
 lost interrupts
Date: Fri, 26 Aug 2016 21:52:56 +0000

 On Fri, Aug 12, 2016 at 05:40:00AM +0000, ryan.brackenbury%gmail.com@localhost wrote:
  > Making simultaneous reads of kernel parameters can cause deadlock
  > of some kernel I/O. Programs trying to read/write to the same
  > kernel parameters after this time are blocked, and hang on I/O
  > indefinitely - these show 'D' in the run status field in top/ps
  > aux.
 
 What are "kernel parameters"? Are you talking just about envstat? Or
 sysctl? Or the combination of the two? Or...?
 
  > Control-C's are lost after this point, and other interrupts become
  > unpredictable or unresponsive. If 'zombie' processes waiting on
  > kern I/O build up, this further causes a system crash.
 
 Those aren't zombies; zombies have state 'Z'.
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost