Messages in this thread | | | From | Christian Lamparter <> | Subject | Re: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available | Date | Sat, 10 Mar 2012 01:52:27 +0100 |
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On Saturday 10 March 2012 00:36:59 Greg KH wrote: > On Fri, Mar 09, 2012 at 11:30:24PM +0100, Christian Lamparter wrote: > > This patch fixes a regression which was introduced by: > > "PM: Print a warning if firmware is requested when tasks are frozen" > > > > request_firmware_nowait does not stall in any system resume paths. > > Therefore, I think it is perfectly save to use request_firmware_nowait > > from at least the ->complete() callback. > > Is there code somewhere in the kernel that wants to do this? uum, yes: The USB subsystem [Good thing, I'm already talking to you! :-D]
Take a look at drivers/usb/core/usb.c:
the ->complete callback is registered to usb_dev_complete(dev*), which is just a lengthy wrapper for usb_resume(dev, PMSG_ON).
Now, let's switch to drivers/usb/core/driver.c:
usb_resume calls do_unbind_rebind(udev, DO_REBIND) and there we go... So any usb driver which uses request_firmware_nowait in .probe is a possible target for the warning.
The one I stumbled across is the pcmcia subsystem. Currently it tries to rebind the devices during ->resume but I have already sent a patch to postpone that till the ->complete callback comes in. <http://lkml.org/lkml/2012/3/3/101>
> Has commit a144c6a broken it somehow that this fix would resolve it? When I read the commit, it only talked only about broken drivers doing "request_firmware" during .probe. But it does not mention what should be done with "request_firmware_nowait" in such a case at all. I think it was just an oversight from all involved parties that just got noticed now.
> > Signed-off-by: Christian Lamparter <chunkeey@googlemail.com> > > --- > > drivers/base/firmware_class.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c > > index 6c9387d..017e020 100644 > > --- a/drivers/base/firmware_class.c > > +++ b/drivers/base/firmware_class.c > > @@ -535,7 +535,7 @@ static int _request_firmware(const struct firmware **firmware_p, > > > > read_lock_usermodehelper(); > > > > - if (WARN_ON(usermodehelper_is_disabled())) { > > + if (WARN_ON(usermodehelper_is_disabled() && !(nowait && uevent))) { > > What does uevent have to do with things here? I found this "useful" comment about uevent in request_firmware_nowait's kdocs: * @uevent: sends uevent to copy the firmware image if this flag * is non-zero else the firmware copy must be done manually. I think this flag controls whenever we want to sent a firmware request event to the usermodehelper... [No idea why this should ever be 'false', maybe there is a good use-case for it when the firmware is built-in... But anyway let's just say I'm as ignorant as everybody else and I haven't got a single clue about it.]
Regards, Christian
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