Re: [PATCH v5 1/5] firmware: document user mode helper lock usage

From: Luis R. Rodriguez
Date: Wed Oct 05 2016 - 16:46:36 EST

On Fri, Sep 23, 2016 at 10:13:44AM +0200, Daniel Wagner wrote:
> On 09/22/2016 04:36 AM, Ming Lei wrote:
> >On Sat, Sep 10, 2016 at 6:14 AM, Luis R. Rodriguez <mcgrof@xxxxxxxxxx> wrote:
> >>On Fri, Sep 09, 2016 at 02:12:20PM +0200, Daniel Wagner wrote:
> >>>From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
> >>>
> >>>The lock is also used to generate warnings when a direct
> >>>firmware load is requested too early.
> >>
> >>I've determined the firmware cache lets us bail out of this
> >>consideration now. If Ming agrees with the logic we don't need this
> >>patch and you can continue as you had intended. Sorry for the trouble.
> >
> >IMO it is helpful to add comment about using the lock for direct loading,
> >and we can sort it out in future if anyone want to improve it.
> >
> >So for this patch, I am fine.
> Sorry, I am a bit confused now. What is the consensus here:
> a) add a comment to _request_firmware() as in this patch #1 v5

The adding a comment note from Daniel was that the UMH lock is *not*
needed on the direct firmware loading case, he's lazy to remove it
now so he'll just add a comment.

> b) move the umh locking to fw_load_from_user_helper() as in
> patch #1 v4

This is fine and IMHO the non-lazy approach.

To be clear -- I did my own vetting of the removal of the lock by
inspecting the original purpose of the UMH lock being added on the
history Linux git tree, having a secondary review of that would be
appreciated as well.