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, 2 insertions, 0 deletions

diff --git a/sys/kern/subr_turnstile.c b/sys/kern/subr_turnstile.c
index 2aad232..114b139 100644
--- a/sys/kern/subr_turnstile.c
+++ b/sys/kern/subr_turnstile.c
@@ -733,6 +733,7 @@ turnstile_wait(struct turnstile *ts, struct thread *owner, int queue)
 	td->td_tsqueue = queue;
 	td->td_blocked = ts;
 	td->td_lockname = lock->lo_name;
+	td->td_blktick = ticks;
 	TD_SET_LOCK(td);
 	mtx_unlock_spin(&tc->tc_lock);
 	propagate_priority(td);
@@ -925,6 +926,7 @@ turnstile_unpend(struct turnstile *ts, int owner_type)
 		MPASS(TD_CAN_RUN(td));
 		td->td_blocked = NULL;
 		td->td_lockname = NULL;
+		td->td_blktick = 0;
 #ifdef INVARIANTS
 		td->td_tsqueue = 0xff;
 #endif