Add a new ddb command 'show sleepq'. It takes a wait channel as an

argument and looks for a sleep queue associated with that wait channel.
If it finds one it will display information such as the list of threads
sleeping on that queue.  If it can't find a sleep queue for that wait
channel, then it will see if that address matches any of the active
sleep queues.  If so, it will display information about the sleepq at the
specified address.

1 files changed, 64 insertions, 2 deletions

diff --git a/sys/kern/subr_sleepqueue.c b/sys/kern/subr_sleepqueue.c
index 8443a7f..378fc69 100644
--- a/sys/kern/subr_sleepqueue.c
+++ b/sys/kern/subr_sleepqueue.c
@@ -59,11 +59,12 @@
  * variables.
  */
 
-#include "opt_sleepqueue_profiling.h"
-
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_sleepqueue_profiling.h"
+#include "opt_ddb.h"
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/lock.h>
@@ -77,6 +78,10 @@ __FBSDID("$FreeBSD$");
 #include <sys/sleepqueue.h>
 #include <sys/sysctl.h>
 
+#ifdef DDB
+#include <ddb/ddb.h>
+#endif
+
 /*
  * Constants for the hash table of sleep queue chains.  These constants are
  * the same ones that 4BSD (and possibly earlier versions of BSD) used.
@@ -842,3 +847,60 @@ sleepq_abort(struct thread *td)
 	sleepq_remove(td, wchan);
 	mtx_lock_spin(&sched_lock);
 }
+
+#ifdef DDB
+DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+	struct lock_object *lock;
+	struct thread *td;
+	void *wchan;
+	int i;
+
+	if (!have_addr)
+		return;
+
+	/*
+	 * First, see if there is an active sleep queue for the wait channel
+	 * indicated by the address.
+	 */
+	wchan = (void *)addr;
+	sc = SC_LOOKUP(wchan);
+	LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
+		if (sq->sq_wchan == wchan)
+			goto found;
+
+	/*
+	 * Second, see if there is an active sleep queue at the address
+	 * indicated.
+	 */
+	for (i = 0; i < SC_TABLESIZE; i++)
+		LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
+			if (sq == (struct sleepqueue *)addr)
+				goto found;
+		}
+
+	db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
+	return;
+found:
+	db_printf("Wait channel: %p\n", sq->sq_wchan);
+#ifdef INVARIANTS
+	db_printf("Queue type: %d\n", sq->sq_type);
+	if (sq->sq_lock) {
+		lock = &sq->sq_lock->mtx_object;
+		db_printf("Associated Interlock: %p - (%s) %s\n", lock,
+		    LOCK_CLASS(lock)->lc_name, lock->lo_name);
+	}
+#endif
+	db_printf("Blocked threads:\n");
+	if (TAILQ_EMPTY(&sq->sq_blocked))
+		db_printf("\tempty\n");
+	else
+		TAILQ_FOREACH(td, &sq->sq_blocked, td_slpq) {
+			db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
+			    td->td_tid, td->td_proc->p_pid,
+			    td->td_proc->p_comm);
+		}	
+}
+#endif