Re: Linux 3.0 release

On Fri, 22 Jul 2011 23:26:29 +0200
Francois Romieu [off-list ref] wrote:

Stephen Hemminger [off-list ref] :

quoted

This a regression which probably began with

commit e22bee782b3b00bd4534ae9b1c5fb2e8e6573c5c
Author: Tejun Heo [off-list ref]
Date:   Tue Jun 29 10:07:14 2010 +0200

    workqueue: implement concurrency managed dynamic worker pool

Before that it was perfectly legal for link watch code to
call schedule_delayed_work from IRQ. This should be allowable;
the code to manage the worker pool should handle it.

I beg to differ: see Ben's first report
(http://lists.openwall.net/netdev/2011/05/04/183).
                                       ^^

One of the code path in the netif_carrier code leads it to try and disable
a late workqueue to reenable it immediately (mod_workqueue anyone ?):
netif_carrier_on
-> linkwatch_fire_event
   -> linkwatch_schedule_work
      -> cancel_delayed_work
         -> del_timer_sync

The del_timer_sync has been here for ages. Afaiks it is not a new pool code
nor a schedule_delayed_work only problem.

That path can be fixed by calling _cancel_delayed_work() instead.