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Jason Ekstrand authored
If the driver was not fully loaded, we may still have globals lying around. If we don't tear those down in i915_exit(), we'll leak a bunch of memory slabs. This can happen two ways: use_kms = false and if we've run mock selftests. In either case, we have an early exit from i915_init which happens after i915_globals_init() and we need to clean up those globals. The mock selftests case is especially sticky. The load isn't entirely a no-op. We actually do quite a bit inside those selftests including allocating a bunch of mock objects and running tests on them. Once all those tests are complete, we exit early from i915_init(). Perviously, i915_init() would return a non-zero error code on failure and a zero error code on success. In the success case, we would get to i915_exit() and check i915_pci_driver.driver.owner to detect if i915_init exited early and do nothing. In the failure case, we would fail i915_init() but there would be no opportunity to clean up globals. The most annoying part is that you don't actually notice the failure as part of the self-tests since leaking a bit of memory, while bad, doesn't result in anything observable from userspace. Instead, the next time we load the driver (usually for next IGT test), i915_globals_init() gets invoked again, we go to allocate a bunch of new memory slabs, those implicitly create debugfs entries, and debugfs warns that we're trying to create directories and files that already exist. Since this all happens as part of the next driver load, it shows up in the dmesg-warn of whatever IGT test ran after the mock selftests. While the obvious thing to do here might be to call i915_globals_exit() after selftests, that's not actually safe. The dma-buf selftests call i915_gem_prime_export which creates a file. We call dma_buf_put() on the resulting dmabuf which calls fput() on the file. However, fput() isn't immediate and gets flushed right before syscall returns. This means that all the fput()s from the selftests don't happen until right before the module load syscall used to fire off the selftests returns which is after i915_init(). If we call i915_globals_exit() in i915_init() after selftests, we end up freeing slabs out from under objects which won't get released until fput() is flushed at the end of the module load syscall. The solution here is to let i915_init() return success early and detect the early success in i915_exit() and only tear down globals and nothing else. This way the module loads successfully, regardless of the success or failure of the tests. Because we've not enumerated any PCI devices, no device nodes are created and it's entirely useless from userspace. The only thing the module does at that point is hold on to a bit of memory until we unload it and i915_exit() is called. Importantly, this means that everything from our selftests has the ability to properly flush out between i915_init() and i915_exit() because there is at least one syscall boundary in between. In order to handle all the delicate init/exit cases, we convert the whole thing to a table of init/exit pairs and track the init status in the new init_progress global. This allows us to ensure that i915_exit() always tears down exactly the things that i915_init() successfully initialized. We also allow early-exit of i915_init() without failure by an init function returning > 0. This is useful for nomodeset, and selftests. For the mock selftests, we convert them to always return 1 so we get the desired behavior of the driver always succeeding to load the driver and then properly tearing down the partially loaded driver. v2 (Tvrtko Ursulin): - Guard init_funcs[i].exit with GEM_BUG_ON(i >= ARRAY_SIZE(init_funcs)) v2 (Daniel Vetter): - Update the docstring for i915.mock_selftests Signed-off-by:
Jason Ekstrand <jason@jlekstrand.net> Reviewed-by:
Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Signed-off-by:
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