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

[Ryan Brackenbury <ryan.brackenbury%gmail.com@localhost>]

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

From: Ryan Brackenbury <ryan.brackenbury%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/51412: Syscall I/O race condition leads to deadlock and lost interrupts
Date: Sun, 28 Aug 2016 12:57:33 -0400

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  >What are "kernel parameters"? Are you talking just about envstat? Or
  >sysctl? Or the combination of the two? Or...?
 My experience here comes from a sysadmin/hobbyist (not kern hacker)
 perspective, so I might be using the wrong terminology. I am referring to
 the kernel values and variables set/retrieved via ioctls from sysctl and
 envstat - such as those in the MIB for sysctl. I am not sure how sysctl and
 envstat vary about how they both interact with the kernel, so I can't
 pretend to have a more in-depth understanding than that above.
 
 What I do know is that using one and/or the other command can influence the
 execution of the other. For example: if retrieving values with envstat
 deadlocks on I/O, calling sysctl can be enough to unblock envstat (and vice
 versa). In my experience, also running either program concurrent with
 another copy of the same has caused these I/O blocks. So to answer your
 question - either envstat, or sysctl, or a combination of the two is
 sufficient.
 
 > Those aren't zombies; zombies have state 'Z'.
 Yes; it just seemed like an appropriate way to compare them, since they
 were un-killable but still using up system resources.
 
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 <div dir=3D"ltr"><span style=3D"font-size:12.8px">=C2=A0&gt;What are &quot;=
 kernel parameters&quot;? Are you talking just about envstat? Or</span><br s=
 tyle=3D"font-size:12.8px"><span style=3D"font-size:12.8px">=C2=A0&gt;sysctl=
 ? Or the combination of the two? Or...?<br></span>My experience here comes =
 from a sysadmin/hobbyist (not kern hacker) perspective, so I might be using=
  the wrong terminology. I am referring to the kernel values and variables s=
 et/retrieved via ioctls from sysctl and envstat - such as those in the MIB =
 for sysctl. I am not sure how sysctl and envstat vary about how they both i=
 nteract with the kernel, so I can&#39;t pretend to have a more in-depth und=
 erstanding than that above.=C2=A0<br><br>What I do know is that using one a=
 nd/or the other command can influence the execution of the other. For examp=
 le: if retrieving values with envstat deadlocks on I/O, calling sysctl can =
 be enough to unblock envstat (and vice versa). In my experience, also runni=
 ng either program concurrent with another copy of the same has caused these=
  I/O blocks. So to answer your question - either envstat, or sysctl, or a c=
 ombination of the two is sufficient.<br><br>&gt;=C2=A0<span style=3D"font-s=
 ize:12.8px">Those aren&#39;t zombies; zombies have state &#39;Z&#39;.<br></=
 span>Yes; it just seemed like an appropriate way to compare them, since the=
 y were un-killable but still using up system resources.<br><div class=3D"gm=
 ail_extra"><div class=3D"gmail_quote"><br></div></div></div>
 
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