Re: 3.17-rc1: leds blink workqueue causes sleeping BUGs
From: Samuel Thibault
Date: Mon Aug 25 2014 - 17:32:44 EST
Sabrina Dubroca, le Mon 25 Aug 2014 23:13:40 +0200, a écrit :
> 2014-08-19, 13:06:07 -0400, Valdis.Kletnieks@xxxxxx wrote:
> > On Sat, 16 Aug 2014 20:27:01 -0700, Hugh Dickins said:
> > > Can we safely revert your 8b37e1bef5a6 ("leds: convert blink timer to
> > > workqueue"), or have there been other changes which now depend upon it?
> > I suspect there's something else busted. I hand-reverted that patch, and I *still*
> > see the following lockdep whine that looks related (as it talks about
> > leddev_list_lock). next-0811 was OK, looks like next-0815 and -0818 had this....
> I had a look at the code, led_trigger_event calls vt_led_set, which
> calls led_trigger_event again.
Yes, that is expected: the vt::* leds actually generate the
corresponding vt-* trigger events, which are used by the various
input*::* leds. We could indeed have a loop if the user was making the
VT::* leds use the vt-* trigger, but otherwise it's safe since it's a
different trigger. We can add code to prevent the user from building
loops, but otherwise it's a false positive.
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