On Tue, Nov 22, 2022 at 9:31 AM Daniel Latypov dlatypov@google.com wrote:
On Sat, Nov 19, 2022 at 12:13 AM David Gow davidgow@google.com wrote:
KUnit does a few expensive things when enabled. This hasn't been a problem because KUnit was only enabled on test kernels, but with a few people enabling (but not _using_) KUnit on production systems, we need a runtime way of handling this.
Provide a 'kunit_running' static key (defaulting to false), which allows us to hide any KUnit code behind a static branch. This should reduce the performance impact (on other code) of having KUnit enabled to a single NOP when no tests are running.
Note that, while it looks unintuitive, tests always run entirely within __kunit_test_suites_init(), so it's safe to decrement the static key at the end of this function, rather than in __kunit_test_suites_exit(), which is only there to clean up results in debugfs.
Signed-off-by: David Gow davidgow@google.com
Reviewed-by: Daniel Latypov dlatypov@google.com
I didn't know anything about the static key support in the kernel before this patch. But from what I read and saw of other uses, this looks good to me.
One small question/nit about how we declare the key below.
<snip>
+/* Static key: true if any KUnit tests are currently running */ +extern struct static_key_false kunit_running;
Is there any documented preference between this and DECLARE_STATIC_KEY_FALSE(kunit_running); ?
I see 89 instances of this macro and 45 of `extern struct static_key_false`. So I'd vote for the macro since it seems like the newer approach and more common.
Yeah, there was no particular reason I put 'extern struct static_key_false'. I'll change it to DECLARE_STATIC_KEY_FALSE in v3.
Cheers, -- David