On Thu, Jul 28, 2022 at 4:42 AM David Gow <davidgow@xxxxxxxxxx> wrote: > > On Thu, Jul 21, 2022 at 4:29 AM Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote: > > > > On Wed, Jul 20, 2022 at 05:26:02PM +0800, David Gow wrote: > > > On Wed, Jul 20, 2022 at 1:58 AM Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote: > > > > > > > > On Wed, Jul 13, 2022 at 08:24:32AM -0700, Daniel Latypov wrote: > > > > > On Tue, Jul 12, 2022 at 5:52 PM David Gow <davidgow@xxxxxxxxxx> wrote: > > > > > > > > > > > > The new KUnit module handling has KUnit test suites listed in a > > > > > > .kunit_test_suites section of each module. This should be loaded when > > > > > > the module is, but at the moment this only happens if KUnit is built-in. > > > > > > > > > > > > Also load this when KUnit is enabled as a module: it'll not be usable > > > > > > unless KUnit is loaded, but such modules are likely to depend on KUnit > > > > > > anyway, so it's unlikely to ever be loaded needlessly. > > > > > > > > > > This seems reasonable to me. > > > > > > > > > > Question: what happens in this case? > > > > > 1. insmod <test-module> > > > > > 2. insmod kunit > > > > > 3. rmmod <test-module> > > > > > > > > > > I think on 3, we'll call the cleanup code, __kunit_test_suites_exit(), > > > > > for <test-module>, I think? > > > > > But we never called __kunit_test_suites_init(). > > > > > My fear is what breaks as a result of this precondition break. > > > > > > I don't think this should be possible: any module with KUnit tests > > > will depend on the 'kunit' module (or, at least, kunit symbols), so > > > shouldn't load without kunit already present. > > > > > > If modprobe is used, kunit will automatically be loaded. If insmod is > > > used directly, loading the first module should error out with > > > something like: > > > [ 82.393629] list_test: loading test module taints kernel. > > > [ 82.409607] list_test: Unknown symbol kunit_binary_ptr_assert_format (err -2) > > > [ 82.409657] list_test: Unknown symbol kunit_do_failed_assertion (err -2) > > > [ 82.409799] list_test: Unknown symbol kunit_binary_assert_format (err -2) > > > [ 82.409820] list_test: Unknown symbol kunit_unary_assert_format (err -2) > > > insmod: ERROR: could not insert module > > > /lib/modules/5.19.0-rc1-15284-g9ec67db0c271/kernel/lib/list-test.ko: > > > Unknown symbol in module > > > > This can be fixed with a request_module() call. And since this is a > > generic requirement, you can have the wrappers do it for you. > > > > I'm not convinced that this is worth the trouble, particularly since > KUnit needs to be loaded already before any test-specific code in a > module is run. _Maybe_ we could put it in the code which looks for the > .kunit_test_suites section, but even then it seems like a bit of an > ugly hack. > > Personally, I'm not particularly concerned about test modules failing > to load if KUnit isn't already present -- if people want all of a > module's dependencies loaded, that's what modprobe is for. > > That being said, if you feel particularly strongly about it, this is > something we can look at. Let's do so in a separate patch though: this > one does fix a regression as-is. I agree. We need a fix for 3d6e44623841 to go in for 5.20 - we've gotten several complaints about it. This patch seems to accomplish that. I am not an expert on the module stuff by any means, so I am absolutely open to continuing this discussion in a follow-up patch, but I think we need this fix now. If no one objects, I am going to ask Shuah to take this patch. > > > Maybe you could get into some trouble by force-removing modules at > > > various points, but you're in undefined behaviour generally at that > > > point, so I don't think there's much point going out-of-our-way to try > > > to support that. > > > > You can prevent that by refcounting the kunit module / symbols, by each test. > > > > Again, I don't think KUnit is any more special than any other module > here. I don't think we need to do this ourselves, as it shouldn't be > possible to remove kunit without first removing any dependent modules. > > Of course, happy to look into this again if anyone can come up with an > actual crash, but I'd rather get this fix in first. At the very least, > this patch shouldn't introduce any _new_ issues. Sounds good. I will send my Reviewed-by in a separate email, as per usual. Cheers
