Re: [RESEND][PATCH] Bluetooth: Make request workqueue freezable

From: Alan Stern
Date: Tue May 19 2015 - 10:26:53 EST


On Tue, 19 May 2015, Takashi Iwai wrote:

> > > I am not convinced. Now we are hacking the Bluetooth core layer
> > > (which has nothing to do with the drivers suspend/resume or
> > > probe) to do something different so that we do not see this
> > > warning.
> > >
> > > I can not do anything about the platform in question choosing a
> > > unplug/replug for suspend/resume instead of having a proper USB
> > > suspend and resume handling. That is pretty much out of our
> > > control.

Actually one can do something about this. I mean, one _can_ implement
proper USB suspend and resume handling in the Bluetooth driver. At
this point the details aren't clear to me, but perhaps if the driver in
question had a reset_resume callback then it might work better.

> > > I would rather have the USB subsystem delay the probe()
> > > callback if we tell it to.

This is possible. I am not sure it would be the right thing to do,
though. What happens if the probe routine gets called early on during
the boot-up procedure, before userspace is up and running? The same
thing should happen here.

> > > Of just have request_firmware()
> > > actually sleep until userspace is ready. Seriously, why is
> > > request_firmware not just sleeping for us.

It won't work. The request_firmware call is part of the probe
sequence, which in turn is part of the resume sequence. Userspace
doesn't start running again until the resume sequence is finished. If
request_firmware waited for userspace, it would hang.

Alan Stern

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