linux-kernel - Re: btusb "firmware request while host is not available" at resume

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Date:   Tue, 3 Oct 2017 18:21:17 -0700
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Gabriel C <nix.or.die@...il.com>, Tejun Heo <tj@...nel.org>,
        "Gustavo F. Padovan" <gustavo@...ovan.org>,
        Sukumar Ghorai <sukumar.ghorai@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "bluez mailin list (linux-bluetooth@...r.kernel.org)" 
        <linux-bluetooth@...r.kernel.org>
Subject: Re: btusb "firmware request while host is not available" at resume

On Tue, Oct 3, 2017 at 5:20 PM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> the ordering devised currently there is:
>
>   o device driver pm ops called
>   o notifier for suspend issued - *going to suspend*
>   o userspace frozen
>   o filesystem freeze
>
> On the way back up this order is inverted:
>
>   o filesystem freeze
>   o userspace frozen
>   o notifier for suspend issued - *going to suspend*
>   o device driver pm ops called

Fortunately I had it a tad bit wrong, but in a good way. Our ordering
on our way down is:

 o notifier for suspend issued - *going to suspend*
 o userspace frozen
 o filesystem freeze (new, being proposed)
 o device driver pm ops called

Then on our way up:

  o device driver pm ops called
  o filesystem thaw
  o userspace thaw
  o notifier for resume issued - *thawing*

So the driver callbacks get called *later*, so anything called in
notifiers do get a chance to quiesce things properly.

  Luis