On 11/12/2010 10:13 AM, Tejun Heo wrote:
Hello,
On 11/12/2010 07:06 PM, Ben Greear wrote:
On 11/12/2010 02:15 AM, Tejun Heo wrote:
Please note that under those circumstances, what's guaranteed is
forward-progress for workqueues which are used during memory reclaim.
Continuously scheduling works which will in turn pile up on rtnl_lock
is akin to constantly allocating memory while something holding
rtnl_lock is blocked due to memory pressure. Correctness-wise, it
isn't necessarily deadlock but the only possible recourse is OOM.
From looking at the wireless code, since sdata is stopped, the
'work' isn't going to actually do anything anyway.
Is there a way to clear the work from the work-queue w/out
requiring any locks that a running worker thread might hold?
(So instead of flush_work, we could call something like "remove_all_work"
and not block on the worker thread that may currently be trying to
acquire rtnl?)
Hmmm... there's cancel_work_sync(). It'll cancel if the work is
pending and wait for completion if it's already running. BTW, which
That would help, but it *might* be possible that the worker thread is
currently active. That work shouldn't be asking for rtnl, as far as I can
tell, so maybe that's OK. I'll give that a try in a bit.
part of code are we talking about? Can you please attach full thread
dump at deadlock?
The problem code seems to be flush_work() call in ieee80211_do_stop()
in net/mac80211/iface.c. RTNL is held when the flush_work() method
is called.
I've seen this apparently deadlock with a worker process trying to
call the wireless_nlevent_process method in net/wireless/wext-core.c
(it acquires rtnl).
Please let me know if you saw the previous thread dumps I sent in this thread.
Those were only for processes blocked > 120secs. I can probably get
a full sysrq dump if you want that instead.
Thanks,
Ben
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
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