misc/166340: Process under FreeBSD 9.0 hangs in uninterruptable sleep with apparently no syscall (empty wchan)

[Konstantin Belousov]

The following reply was made to PR kern/166340; it has been noted by GNATS.

From: Konstantin Belousov <kostikbel at gmail.com>
To: Christian Esken <Christian.Esken at trivago.com>
Cc: bug-followup at freebsd.org, avg at freebsd.org
Subject: Re: misc/166340: Process under FreeBSD 9.0 hangs in uninterruptable sleep with apparently no syscall (empty wchan)
Date: Mon, 26 Mar 2012 16:51:42 +0300

 Thank you for the data. Semi-obviously, the callout_stop() call in
 sleepq_check_timeout() have to return 0, otherwise we would not call
 mi_switch() there. But I do not see how this can happen, because
 the callout state, printed from kgdb, still indicates that callout
 is pending. Callout cannot be reset while in sleepq code.
 
 So there are two possible routes to go forward: preferrable is for
 you to extract the self-contained C program that would illustrate
 the issue and send this sample to me. Second is to recompile your
 kernel with INVARIANTS/WITNESS and possibly KTR and see what happen.