Messages in this thread | | | Date | Mon, 22 Nov 2004 11:25:02 +0100 | From | Gerd Knorr <> | Subject | Re: modprobe + request_module() deadlock |
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> > > MODULE_DEPENDS_ON("somemodule"); > > > > On the other hand I don't depend on request_module() waiting for the > > modprobe being finished. So maybe we can solve that with a > > request_module_async()? > > The problem is fairly simple: we don't let you get at the symbols from a > module which hasn't finished initializing yet. This means that a > request_module() inside a module's init() will fail if the requested > module depends on this one. async() will race with init() finishing, so > won't really help.
Hmm, so module loading is not serialized by a lock? I assumed that caused the deadlock in $subject which started this thread ...
> The traditional way to do this has been to have saa7134-empress do its > own probe, and likewise saa7134-dvb.
They can't actually probe themself. It's _one_ PCI device (driven by the saa7134 module) which can handle (among other v4l-related things) the DMA transfer of mpeg streams. That can be used in different ways (or not at all) and the different use cases are handled by the sub-modules.
So the way it is intended to work is that saa7134 has the pci table and gets autoloaded by hotplug, it will have a look at the hardware and then load either saa7134-empress or saa7134-dvb or none of them, so you'll get everything nicely autoloaded.
> Unfortunately, these days modules are not supposed to fail to load > simply because there are no devices, so wild module loading has a real > cost.
Yes, thats exactly the problem. And this is especially true for the saa7134-dvb module as this one has a bunch of dependencies to other modules of the dvb subsystem. Thats why I try to avoid loading them if they are not needed.
> Otherwise I'd be tempted to make multiple aliases load *all* of them, > and solve the problem that way.
Well, that will actually work. You can simply load both saa7134-empress and saa7134-dvb, the saa7134 core module will take care that they can only attach to devices they can actually handle. Drawback is the memory footprint ...
Gerd
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