svn commit: r212506 - head/sys/nfsclient

[Kostik Belousov]

On Sun, Sep 12, 2010 at 09:41:46PM +0100, Robert Watson wrote:
> 
> On Sun, 12 Sep 2010, Konstantin Belousov wrote:
> 
> > Do not fork nfsiod directly from the vop methods. This causes LORs between
> > vnode lock and several locks needed during fork, like fd lock.
> >
> > Instead, schedule the task to be executed in the taskqueue context. We
> > still waiting for the fork to finish, but the context of the thread
> > executing the task does not make real LORs with our vnode lock.
> 
> Does this actually functionally improve things, or is all this complexity 
> about suppressing the lock order reversal?  If we're waiting synchronously 
> for the other thread to launch from the task queue, then the lock order 
> reversal still exists, it's just not visible to WITNESS...  If we had a 
> static analysis tool that could run on lock and sleep/wakeup traces, it 
> would still show a deadlock opportunity.

As I said in commit message, the deadlock should be fixed, because the
taskq thread is executed in the kernel process that should even not have
file descriptors at all.
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