linux-kernel - Re: [RESEND][PATCH] Bluetooth: Make request workqueue freezable

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Date:	Tue, 19 May 2015 19:13:14 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Laura Abbott <labbott@...hat.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Laura Abbott <labbott@...oraproject.org>,
	"Gustavo F. Padovan" <gustavo@...ovan.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	"bluez mailin list (linux-bluetooth@...r.kernel.org)" 
	<linux-bluetooth@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ming Lei <ming.lei@...onical.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	<linux-usb@...r.kernel.org>
Subject: Re: [RESEND][PATCH] Bluetooth: Make request workqueue freezable

At Tue, 19 May 2015 10:26:46 -0400 (EDT),
Alan Stern wrote:
> 
> > > >  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.

Note that the recent request_firmware() doesn't need the user-space
invocation (unless the fallback is explicitly enabled) but loads the
file directly.  And, request_firmware() for the cached data is valid
to be called in the resume path.


Takashi
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