Re: [PATCH v4 1/4] firmware: Move umh locking code into fw_load_from_user_helper()

[Ming Lei]

On Fri, Sep 9, 2016 at 11:39 AM, Luis R. Rodriguez <mcgrof@xxxxxxxxxx> wrote:
> On Sep 8, 2016 6:22 PM, "Ming Lei" <ming.lei@xxxxxxxxxxxxx> wrote:
>>
>> On Fri, Sep 9, 2016 at 4:11 AM, Luis R. Rodriguez <mcgrof@xxxxxxxxxx>
>> wrote:
>> > On Thu, Sep 08, 2016 at 11:37:54PM +0800, Ming Lei wrote:
>> >> On Wed, Sep 7, 2016 at 4:45 PM, Daniel Wagner <wagi@xxxxxxxxx> wrote:
>> >> > From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
>> >> >
>> >> > When we load the firmware directly we don't need to take the umh
>> >> > lock.
>> >>
>> >> I am wondering if it can be wrong.
>> >
>> > If you disable the firmware UMH why would we need to lock if the lock is
>> > being
>> > shown only used for the firmare UMH ?
>> >
>> >> Actually in case of firmware loading, the usermode helper lock doesn't
>> >> only mean the user helper is usable, and it also may serve to mark the
>> >> filesystem/block device is ready for firmware loading, and of couse
>> >> direct
>> >> loading need fs/block to be ready too.
>> >
>> > Yes but that's a race I've identified a while ago present even if you
>> > use initramfs *and*
>> > use kernel_read_file_from_path() on any part of the kernel [0], I
>> > proposed a possible
>>
>> Actualy I mean the situation of suspend vs. resume, and some drivers
>> still may not benefit from firmware loading cache when requesting loading
>> in .resume(), at that time it is still too early for direct loading.
>> With UMH lock,
>> we can get a warning or avoid the issue.
>
> Agreed, but that would seem odd and perhaps misleading to have a try lock
> for UMH when no firmware UMH code is enabled. This should probably made
> clear in comments for now as to why we have it then and we should just mark

That is very helpful, :-)

> a TODO item to generalize this to a common freezer check. Surprised we don't
> have one yet. Rafael ?
>
>   Luis