Re: deadlocks if use htb

Jarek Poplawski
2008-12-11T08:46:35Z

On Wed, Dec 10, 2008 at 06:14:28PM +0300, Badalian Vyacheslav wrote:
> Hello again! Sorry for long away.

Hi!

> I was go away from this work for long time.
>
> May we return to this bug?
> Servers at last stable kernel 2.6.27.8
> HZ=1000, HR=off, DynamicTicks=off, hysteresis=1
> Sorry - no patched, update do not i. Do you have fresh patches or ideas
> for tests?

Not much, but I can have if you only are willing to test them...
I attach below a patch which combines 2 patches I sent yesterday to
netdev (PATCH 7/6 and 8/6) vs. 2.6.27.7 (named testing patch #3 here).

You can still try the testing patch #2 I sent previously (quoted below)
with or without this new #3 patch.

Thanks,
Jarek P.

> Also debug "Debug object operations" and "Debug timer objects" is on but
> i not see additional information at dump.
>
> Thanks!
>
> That dump:
> [ 1500.932813] BUG: NMI Watchdog detected LOCKUP on CPU3, ip c0208ed9,
> registers:
> [ 1500.932813] Modules linked in: cls_u32 sch_sfq sch_htb netconsole
> e1000e e1000 i2c_i801
> [ 1500.932813]
> [ 1500.932813] Pid: 0, comm: swapper Not tainted (2.6.27-gentoo-r5-fw #1)
> [ 1500.932813] EIP: 0060:[<c0208ed9>] EFLAGS: 00000082 CPU: 3
> [ 1500.932813] EIP is at rb_insert_color+0x29/0xf0
...
> > --- (testing patch #2)
> >
> > net/sched/sch_htb.c | 8 +++++++-
> > 1 files changed, 7 insertions(+), 1 deletions(-)
> >
> > diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
> > index 30c999c..ff9e965 100644

-----------> (testing patch #3)

diff -Nurp a2.6.27.7/net/sched/sch_htb.c b2.6.27.7/net/sched/sch_htb.c
--- a2.6.27.7/net/sched/sch_htb.c 2008-12-11 08:16:16.000000000 +0000
+++ b2.6.27.7/net/sched/sch_htb.c 2008-12-11 08:20:27.000000000 +0000
@@ -696,12 +696,13 @@ static void htb_charge_class(struct htb_
* next pending event (0 for no event in pq).
* Note: Applied are events whose have cl->pq_key <= q->now.
*/
-static psched_time_t htb_do_events(struct htb_sched *q, int level)
+static psched_time_t htb_do_events(struct htb_sched *q, int level,
+ unsigned long start)
{
/* don't run for longer than 2 jiffies; 2 is used instead of
1 to simplify things when jiffy is going to be incremented
too soon */
- unsigned long stop_at = jiffies + 2;
+ unsigned long stop_at = start + 2;
while (time_before(jiffies, stop_at)) {
struct htb_class *cl;
long diff;
@@ -720,8 +721,8 @@ static psched_time_t htb_do_events(struc
if (cl->cmode != HTB_CAN_SEND)
htb_add_to_wait_tree(q, cl, diff);
}
- /* too much load - let's continue on next jiffie */
- return q->now + PSCHED_TICKS_PER_SEC / HZ;
+ /* too much load - let's continue on next jiffie (including above) */
+ return q->now + 2 * PSCHED_TICKS_PER_SEC / HZ;
}

/* Returns class->node+prio from id-tree where classe's id is >= id. NULL
@@ -880,6 +881,7 @@ static struct sk_buff *htb_dequeue(struc
struct htb_sched *q = qdisc_priv(sch);
int level;
psched_time_t next_event;
+ unsigned long start_at;

/* try to dequeue direct packets as high prio (!) to minimize cpu work */
skb = __skb_dequeue(&q->direct_queue);
@@ -892,6 +894,7 @@ static struct sk_buff *htb_dequeue(struc
if (!sch->q.qlen)
goto fin;
q->now = psched_get_time();
+ start_at = jiffies;

next_event = q->now + 5 * PSCHED_TICKS_PER_SEC;
q->nwc_hit = 0;
@@ -901,14 +904,14 @@ static struct sk_buff *htb_dequeue(struc
psched_time_t event;

if (q->now >= q->near_ev_cache[level]) {
- event = htb_do_events(q, level);
+ event = htb_do_events(q, level, start_at);
if (!event)
event = q->now + PSCHED_TICKS_PER_SEC;
q->near_ev_cache[level] = event;
} else
event = q->near_ev_cache[level];

- if (event && next_event > event)
+ if (next_event > event)
next_event = event;

m = ~q->row_mask[level];