On 3/2/2015 5:09 PM, Doug Ledford wrote:
On Sun, 2015-03-01 at 08:47 +0200, Erez Shitrit wrote:
On 2/26/2015 6:27 PM, Doug Ledford wrote:
@@ -1037,6 +1038,7 @@ static void __ipoib_ib_dev_flush(struct ipoib_dev_priv *priv,
if (level == IPOIB_FLUSH_LIGHT) {
ipoib_mark_paths_invalid(dev);
ipoib_mcast_dev_flush(dev);
+ ipoib_flush_ah(dev, 0);
Why do you need to call the flush function here?
To remove all of the ah's that were reduced to a 0 refcount by the
previous two functions prior to restarting operations. When we remove
an ah, it calls ib_destroy_ah which calls all the way down into the low
level driver. This was to make sure that old, stale data was removed
all the way down to the card level before we started new queries for
paths and ahs.
Yes. but it is not needed.
That depends on the card. For the modern cards (mlx4, mlx5, qib), it
isn't needed but doesn't hurt either. For older cards (in particular,
mthca), the driver actually frees up card resources at the time of the
call.
Can you please elaborate more here, I took a look in the mthca and
didn't see that.
anyway, what i don't understand is why you need to do that now, the ah
is already in the dead_ah_list so, in at the most 1 sec will be cleared
and if the driver goes down your other hunk fixed that.
The bug happened when the driver was removed (via modprobe -r etc.), and
there were ah's in the dead_ah list, that was fixed by you in the
function ipoib_ib_dev_cleanup, the call that you added here is not
relevant to the bug (and IMHO is not needed at all)
I never said that this hunk was part of the original bug I saw before.
So, the the task of cleaning the dead_ah is already there, no need to
recall it, it will be called anyway 1 sec at the most from now.
You can try that, take of that call, no harm or memory leak will happened.
I have no doubt that it will get freed later. As I said, I never
considered this particular hunk part of that original bug. But, as I
point out above, there is no harm in it for any hardware, and depending
on hardware it can help to make sure there isn't a shortage of
resources. Given that fact, I see no reason to remove it.
I can't see the reason to use the flush not from the stop_ah, meaning
without setting the IPOIB_STOP_REAPER, the flush can send twice the same
work.
No, it can't. The ah flush routine does not search through ahs to find
ones to flush. When you delete neighbors and mcasts, they release their
references to ahs. When the refcount goes to 0, the put routine puts
the ah on the to-be-deleted ah list. All the flush does is take that
list and delete the items. If you run the flush twice, the first run
deletes all the items on the to-be-deleted list, the second run sees an
empty list and does nothing.
As for using flush versus stop: the flush function cancels any delayed
ah_flush work so that it isn't racing with the normally scheduled
when you call cancel_delayed_work to work that can schedule itself, it
is not help, the work can be at the middle of the run and re-schedule
itself...
If it is in the middle of a run and reschedules itself, then it will
schedule itself at precisely the same time we would have anyway, and we
will get flushed properly, so the net result of this particular race is
that we end up doing exactly what we wanted to do anyway.
ah_flush, then flushes the workqueue to make sure anything that might
result in an ah getting freed is done, then flushes, then schedules a
new delayed flush_ah work 1 second later. So, it does exactly what a
flush should do: it removes what there is currently to remove, and in
the case of a periodically scheduled garbage collection, schedules a new
periodic flush at the maximum interval.
It is not appropriate to call stop_ah at this point because it will
cancel the delayed work, flush the ahs, then never reschedule the
garbage collection. If we called stop here, we would have to call start
later. But that's not really necessary as the flush cancels the
scheduled work and reschedules it for a second later.
}
if (level >= IPOIB_FLUSH_NORMAL)
@@ -1100,6 +1102,14 @@ void ipoib_ib_dev_cleanup(struct net_device *dev)
ipoib_mcast_stop_thread(dev, 1);
ipoib_mcast_dev_flush(dev);
+ /*
+ * All of our ah references aren't free until after
+ * ipoib_mcast_dev_flush(), ipoib_flush_paths, and
+ * the neighbor garbage collection is stopped and reaped.
+ * That should all be done now, so make a final ah flush.
+ */
+ ipoib_stop_ah(dev, 1);
+
ipoib_transport_dev_cleanup(dev);
}
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