Messages in this thread | | | Date | Wed, 21 Jan 2009 13:45:14 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] workqueue: not allow recursion run_workqueue |
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On 01/21, Peter Zijlstra wrote: > > On Wed, 2009-01-21 at 17:42 +0800, Lai Jiangshan wrote: > > 1) lockdep will complain when recursion run_workqueue > > 2) works is not run orderly when recursion run_workqueue > > > > 3) BUG! > > We use recursion run_workqueue to hidden deadlock when > > keventd trying to flush its own queue. > > > > It's bug. When flush_workqueue()(nested in a work callback)returns, > > the workqueue is not really flushed, the sequence statement of > > this work callback will do some thing bad. > > > > So we should not allow workqueue trying to flush its own queue. > > The patch looks good, but I'm utterly failing to comprehend this > changelog. What exactly can go wrong (other than the obvious too deep > nest and the fact that lockdep will complain)?
I am confused too.
But the change itself looks good to me, I am only worried if we still have the callers of flush() from within work->func().
> + WARN_ON(cwq->thread == current);
probably BUG_ON() is better, we are going to deadlock in this case.
Oleg.
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