On Mon, Aug 10, 2020 at 4:43 PM Peter Zijlstra peterz@infradead.org wrote:
On Mon, Aug 10, 2020 at 09:32:57PM +0000, Uriel Guajardo wrote:
+static inline void kunit_check_locking_bugs(struct kunit *test,
unsigned long saved_preempt_count)+{
preempt_count_set(saved_preempt_count);+#ifdef CONFIG_TRACE_IRQFLAGS
if (softirq_count())current->softirqs_enabled = 0;elsecurrent->softirqs_enabled = 1;+#endif +#if IS_ENABLED(CONFIG_LOCKDEP)
local_irq_disable();if (!debug_locks) {kunit_set_failure(test);lockdep_reset();}local_irq_enable();+#endif +}
Unless you can guarantee this runs before SMP brinup, that lockdep_reset() is terminally broken.
Good point. KUnit is initialized after SMP is set up, and KUnit can also be built as a module, so it's not a guarantee that we can make. Is there any other way to turn lockdep back on after we detect a failure? It would be ideal if lockdep could still run in the next test case after a failure in a previous one.
I suppose we could only display the first failure that occurs, similar to how lockdep does it. But it could also be useful to developers if they saw failures in subsequent test cases, with the knowledge that those failures may be unreliable.