On Tue, 19 Mar 2024 at 18:49, Mickaël Salaün <mic@xxxxxxxxxxx> wrote: > > Previously, when a kernel test thread crashed (e.g. NULL pointer > dereference, general protection fault), the KUnit test hanged for 30 > seconds and exited with a timeout error. > > Fix this issue by waiting on task_struct->vfork_done instead of the > custom kunit_try_catch.try_completion, and track the execution state by > initially setting try_result with -EINTR and only setting it to 0 if > the test passed. > > Fix kunit_generic_run_threadfn_adapter() signature by returning 0 > instead of calling kthread_complete_and_exit(). Because thread's exit > code is never checked, always set it to 0 to make it clear. > > Fix the -EINTR error message, which couldn't be reached until now. > > This is tested with a following patch. > > Cc: Brendan Higgins <brendanhiggins@xxxxxxxxxx> > Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > Reviewed-by: David Gow <davidgow@xxxxxxxxxx> > Tested-by: Rae Moar <rmoar@xxxxxxxxxx> > Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> > Link: https://lore.kernel.org/r/20240319104857.70783-5-mic@xxxxxxxxxxx > --- > > Changes since v2: > * s/-EFAULT/-EINTR/ in commit message as spotted by Rae. > * Add a comment explaining vfork_done as suggested by David. > * Add David's Reviewed-by. > * Add Rae's Tested-by. > > Changes since v1: > * Add Kees's Reviewed-by. > --- > include/kunit/try-catch.h | 3 --- > lib/kunit/try-catch.c | 19 ++++++++++++------- > 2 files changed, 12 insertions(+), 10 deletions(-) > > diff --git a/include/kunit/try-catch.h b/include/kunit/try-catch.h > index c507dd43119d..7c966a1adbd3 100644 > --- a/include/kunit/try-catch.h > +++ b/include/kunit/try-catch.h > @@ -14,13 +14,11 @@ > > typedef void (*kunit_try_catch_func_t)(void *); > > -struct completion; > struct kunit; > > /** > * struct kunit_try_catch - provides a generic way to run code which might fail. > * @test: The test case that is currently being executed. > - * @try_completion: Completion that the control thread waits on while test runs. > * @try_result: Contains any errno obtained while running test case. > * @try: The function, the test case, to attempt to run. > * @catch: The function called if @try bails out. > @@ -46,7 +44,6 @@ struct kunit; > struct kunit_try_catch { > /* private: internal use only. */ > struct kunit *test; > - struct completion *try_completion; > int try_result; > kunit_try_catch_func_t try; > kunit_try_catch_func_t catch; > diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c > index cab8b24b5d5a..7a3910dd78a6 100644 > --- a/lib/kunit/try-catch.c > +++ b/lib/kunit/try-catch.c > @@ -18,7 +18,7 @@ > void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch) > { > try_catch->try_result = -EFAULT; > - kthread_complete_and_exit(try_catch->try_completion, -EFAULT); > + kthread_exit(0); It turns out kthread_exit() is not exported, so this doesn't work if KUnit is built as a module. I think the options we have are: - Add EXPORT_SYMBOL(kthread_exit). - Keep using out own completion, and kthread_complete_and_exit() - try_get_module() before spawning the thread, and use module_put_and_kthread_exit(). I think all of these would be okay, but I could've missed something. -- David > } > EXPORT_SYMBOL_GPL(kunit_try_catch_throw); > > @@ -26,9 +26,12 @@ static int kunit_generic_run_threadfn_adapter(void *data) > { > struct kunit_try_catch *try_catch = data; > > + try_catch->try_result = -EINTR; > try_catch->try(try_catch->context); > + if (try_catch->try_result == -EINTR) > + try_catch->try_result = 0; > > - kthread_complete_and_exit(try_catch->try_completion, 0); > + return 0; > } > > static unsigned long kunit_test_timeout(void) > @@ -58,13 +61,11 @@ static unsigned long kunit_test_timeout(void) > > void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) > { > - DECLARE_COMPLETION_ONSTACK(try_completion); > struct kunit *test = try_catch->test; > struct task_struct *task_struct; > int exit_code, time_remaining; > > try_catch->context = context; > - try_catch->try_completion = &try_completion; > try_catch->try_result = 0; > task_struct = kthread_create(kunit_generic_run_threadfn_adapter, > try_catch, "kunit_try_catch_thread"); > @@ -75,8 +76,12 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) > } > get_task_struct(task_struct); > wake_up_process(task_struct); > - > - time_remaining = wait_for_completion_timeout(&try_completion, > + /* > + * As for a vfork(2), task_struct->vfork_done (pointing to the > + * underlying kthread->exited) can be used to wait for the end of a > + * kernel thread. > + */ > + time_remaining = wait_for_completion_timeout(task_struct->vfork_done, > kunit_test_timeout()); > if (time_remaining == 0) { > try_catch->try_result = -ETIMEDOUT; > @@ -92,7 +97,7 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context) > if (exit_code == -EFAULT) > try_catch->try_result = 0; > else if (exit_code == -EINTR) > - kunit_err(test, "wake_up_process() was never called\n"); > + kunit_err(test, "try faulted\n"); > else if (exit_code == -ETIMEDOUT) > kunit_err(test, "try timed out\n"); > else if (exit_code) > -- > 2.44.0 >
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