Introduce the new kernel thread called "deadlock resolver".

While the name is pretentious, a good explanation of its targets is
reported in this 17 months old presentation e-mail:
http://lists.freebsd.org/pipermail/freebsd-arch/2008-August/008452.html

In order to implement it, the sq_type in sleepqueues is mandatory and not
only compiled along with INVARIANTS option. Additively, a new sleepqueue
function, sleepq_type() is added, returning the type of the sleepqueue
linked to a wchan.
Three new sysctls are added in order to configure the thread:
debug.deadlkres.slptime_threshold
debug.deadlkres.blktime_threshold
debug.deadlkres.sleepfreq

rappresenting the thresholds for sleep and block time that will lead to
a deadlock matching (when exceeded), while the sleepfreq rappresents the
number of seconds between 2 consecutive thread runnings.
In order to enable the deadlock resolver thread recompile your kernel
with the option DEADLKRES.

Reviewed by:	jeff
Tested by:	pho, Giovanni Trematerra
Sponsored by:	Nokia Incorporated, Sandvine Incorporated
MFC after:	2 weeks

1 files changed, 10 insertions, 1 deletions

diff --git a/share/man/man9/sleepqueue.9 b/share/man/man9/sleepqueue.9
index 36cab69..3c0e9a5 100644
--- a/share/man/man9/sleepqueue.9
+++ b/share/man/man9/sleepqueue.9
@@ -23,7 +23,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 12, 2009
+.Dd January 8, 2010
 .Dt SLEEPQUEUE 9
 .Os
 .Sh NAME
@@ -44,6 +44,7 @@
 .Nm sleepq_sleepcnt ,
 .Nm sleepq_timedwait ,
 .Nm sleepq_timedwait_sig ,
+.Nm sleepq_type ,
 .Nm sleepq_wait ,
 .Nm sleepq_wait_sig
 .Nd manage the queues of sleeping threads
@@ -84,6 +85,8 @@
 .Fn sleepq_timedwait "void *wchan"
 .Ft int
 .Fn sleepq_timedwait_sig "void *wchan" "int signal_caught"
+.Ft int
+.Fn sleepq_type "void *wchan"
 .Ft void
 .Fn sleepq_wait "void *wchan"
 .Ft int
@@ -366,6 +369,12 @@ given a
 .Fa wchan .
 .Pp
 The
+.Fn sleepq_type
+function returns the type of
+.Fa wchan
+associated to a sleepqueue.
+.Pp
+The
 .Fn sleepq_abort ,
 .Fn sleepq_broadcast ,
 and