On Thu, 2017-06-08 at 13:12 -0700, Krister Johansen wrote:
...
> Looking at the gc_task intervals, they started at 663ms when we invoked
> __dst_free(). After that, they increased to 1663, 3136, 5567, 8191,
> 10751, and 14848. The release that set the refcnt to 0 on our dst entry
> occurred after the gc_task was enqueued for 14 second interval so we had
> to wait longer than the warning time in wait_allrefs in order for the
> dst entry to get free'd and the hold on 'lo' to be released.
>
> A simple solution to this problem is to have dst_dev_event() reset the
> gc timer, which causes us to process this list shortly after the
> gc_mutex is relased when dst_dev_event() completes.
>
> Signed-off-by: Krister Johansen <k...@templeofstupid.com>
> ---
> net/core/dst.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/net/core/dst.c b/net/core/dst.c
> index 6192f11..13ba4a0 100644
> --- a/net/core/dst.c
> +++ b/net/core/dst.c
> @@ -469,6 +469,20 @@ static int dst_dev_event(struct notifier_block *this,
> unsigned long event,
> spin_lock_bh(&dst_garbage.lock);
> dst = dst_garbage.list;
> dst_garbage.list = NULL;
> + /* The code in dst_ifdown places a hold on the loopback device.
> + * If the gc entry processing is set to expire after a lengthy
> + * interval, this hold can cause netdev_wait_allrefs() to hang
> + * out and wait for a long time -- until the the loopback
> + * interface is released. If we're really unlucky, it'll emit
> + * pr_emerg messages to console too. Reset the interval here,
> + * so dst cleanups occur in a more timely fashion.
> + */
> + if (dst_garbage.timer_inc > DST_GC_INC) {
> + dst_garbage.timer_inc = DST_GC_INC;
> + dst_garbage.timer_expires = DST_GC_MIN;
> + mod_delayed_work(system_wq, &dst_gc_work,
> + dst_garbage.timer_expires);
> + }
> spin_unlock_bh(&dst_garbage.lock);
>
> if (last)
Looks very nice to me !
Acked-by: Eric Dumazet <eduma...@google.com>
Wei Wan is actually working on a patch series removing all this
dst_garbage list stuff.
