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From: Grant Likely <grant.likely@secretlab.ca>
Subject: Re: [PATCH] driver core: add wait event for deferred probe
To: Arnd Bergmann <arnd@arndb.de>, Haojian Zhuang <haojian.zhuang@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Linus Walleij <linus.walleij@linaro.org>,
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        Patch Tracking <patches@linaro.org>
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Date: Thu, 14 Feb 2013 17:42:40 +0000
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On Thu, 14 Feb 2013 15:57:18 +0000, Arnd Bergmann <arnd@arndb.de> wrote:
> On Thursday 14 February 2013, Haojian Zhuang wrote:
> > If you can change it into code in below, it could work. Otherwise, it
> > always fails.
> >         driver_deferred_probe_enable = true;
> >         driver_deferred_probe_trigger();
> > +      deferred_probe_work_func(NULL);
> >         return 0;
> > 
> > Because deferred_probe_work_func() depends on that deferred_probe is added
> > into deferred_probe_active_list. If driver_deferred_probe_trigger() isn't called
> > first, the deferred uart probe can't be added into active list. So even you call
> > work_func at here, it doesn't help.
> > 
> 
> Would that not cause two instances of the work function to run at the same time?
> That sounds like a source for a lot of problems.

Yes. Even ignoring the problems with device drivers not handling
multithreaded probing well, the current deferred probe wouldn't handle
it well. I could make it support multithreading, but I don't see a whole
lot of value there.

g.

-- 
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.