linux-kernel - Re: [PATCH v5 2/5] firmware: encapsulate firmware loading status

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Message-ID: <20161018215421.GX8651@wotan.suse.de>
Date:   Tue, 18 Oct 2016 23:54:21 +0200
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Daniel Wagner <daniel.wagner@...-carit.de>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Daniel Wagner <wagi@...om.org>, linux-kernel@...r.kernel.org,
        Ming Lei <ming.lei@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Srivatsa S . Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
        "Rafael J . Wysocki" <rjw@...k.pl>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Takashi Iwai <tiwai@...e.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Arend van Spriel <arend.vanspriel@...adcom.com>
Subject: Re: [PATCH v5 2/5] firmware: encapsulate firmware loading status

On Tue, Oct 18, 2016 at 03:30:45PM +0200, Daniel Wagner wrote:
> On 10/10/2016 10:37 PM, Luis R. Rodriguez wrote:
> 
> > >   fw_get_fileystem_firmware()
> > >     fw_finish_direct_load()
> > >       complete_all()
> > > 
> > > 
> > > 2nd request (waiter context)
> > > 
> > > _request_firmware()
> > >   _request_firmware_prepare()
> > >      fw_lookup_allocate_buf()      # finds previously allocated buf
> > >                                    # returns 1 -> wait for loading
> > >      sync_cached_firmware_buf()
> > >         wait_for_completion_interruptible_timeout()
> > 
> > No, that's wait_for_completion_interruptible() not
> >            wait_for_completion_interruptible_timeout()
> 
> I confused that one from _request_firmware_load().

Right and wait_for_completion_interruptible() has no timeout.

> > Also note that we only call sync_cached_firmware_buf()
> > *iff* fw_lookup_and_allocate_buf() returned the 1 -- I mentioned
> > when this happens above. That happens only if we already had the entry on
> > the fw cache. As it stands -- concurrent calls against the same fw name
> > could cause a clash here, as such, the wait_for_completion_interruptible()
> > is indeed still needed.
> > 
> > Further optimizations can be considered later but for indeed, agreed
> > that completion is needed even for the direct fw load case. The timeout
> > though, I don't see a reason for it.
> 
> So I think I found the source of the confusion about fw_umh_wait_timeout().
> When providing a timeout value of 0 you get the
> wait_for_completion_interruptible() version.

I fail to see that, how so? Note that 0 does is not allowed anyway:

static inline long firmware_loading_timeout(void)
{
        return loading_timeout > 0 ? loading_timeout * HZ : MAX_JIFFY_OFFSET;
}

  Luis