On 4/1/21 11:24 PM, Marco Elver wrote:
> On Thu, 1 Apr 2021 at 21:04, Daniel Latypov <dlatypov@xxxxxxxxxx> wrote:
>> > }
>> > #else
>> > static inline bool slab_add_kunit_errors(void) { return false; }
>> > #endif
>> >
>> > And anywhere you want to increase the error count, you'd call
>> > slab_add_kunit_errors().
>> >
>> > Another benefit of this approach is that if KUnit is disabled, there is
>> > zero overhead and no additional code generated (vs. the current
>> > approach).
>>
>> The resource approach looks really good, but...
>> You'd be picking up a dependency on
>> https://lore.kernel.org/linux-kselftest/20210311152314.3814916-2-dlatypov@xxxxxxxxxx/
>> current->kunit_test will always be NULL unless CONFIG_KASAN=y &&
>> CONFIG_KUNIT=y at the moment.
>> My patch drops the CONFIG_KASAN requirement and opens it up to all tests.
>
> Oh, that's a shame, but hopefully it'll be in -next soon.
>
>> At the moment, it's just waiting another look over from Brendan or David.
>> Any ETA on that, folks? :)
>>
>> So if you don't want to get blocked on that for now, I think it's fine to add:
>> #ifdef CONFIG_SLUB_KUNIT_TEST
>> int errors;
>> #endif
>
> Until kunit fixes setting current->kunit_test, a cleaner workaround
> that would allow to do the patch with kunit_resource, is to just have
> an .init/.exit function that sets it ("current->kunit_test = test;").
> And then perhaps add a note ("FIXME: ...") to remove it once the above
> patch has landed.
>
> At least that way we get the least intrusive change for mm/slub.c, and
> the test is the only thing that needs a 2-line patch to clean up
> later.
So when testing internally Oliver's new version with your suggestions (thanks
again for those), I got lockdep splats because slab_add_kunit_errors is called
also from irq disabled contexts, and kunit_find_named_resource will call
spin_lock(&test->lock) that's not irq safe. Can we make the lock irq safe? I
tried the change below and it makde the problem go away. If you agree, the
question is how to proceed - make it part of Oliver's patch series and let
Andrew pick it all with eventually kunit team's acks on this patch, or whatnot.
----8<----
commit ab28505477892e9824c57ac338c88aec2ec0abce
Author: Vlastimil Babka <vbabka@xxxxxxx>
Date: Tue Apr 6 12:28:07 2021 +0200
kunit: make test->lock irq safe
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 49601c4b98b8..524d4789af22 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -515,8 +515,9 @@ kunit_find_resource(struct kunit *test,
void *match_data)
{
struct kunit_resource *res, *found = NULL;
+ unsigned long flags;
- spin_lock(&test->lock);
+ spin_lock_irqsave(&test->lock, flags);
list_for_each_entry_reverse(res, &test->resources, node) {
if (match(test, res, (void *)match_data)) {
@@ -526,7 +527,7 @@ kunit_find_resource(struct kunit *test,
}
}
- spin_unlock(&test->lock);
+ spin_unlock_irqrestore(&test->lock, flags);
return found;
}
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index ec9494e914ef..2c62eeb45b82 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -442,6 +442,7 @@ int kunit_add_resource(struct kunit *test,
void *data)
{
int ret = 0;
+ unsigned long flags;
res->free = free;
kref_init(&res->refcount);
@@ -454,10 +455,10 @@ int kunit_add_resource(struct kunit *test,
res->data = data;
}
- spin_lock(&test->lock);
+ spin_lock_irqsave(&test->lock, flags);
list_add_tail(&res->node, &test->resources);
/* refcount for list is established by kref_init() */
- spin_unlock(&test->lock);
+ spin_unlock_irqrestore(&test->lock, flags);
return ret;
}
@@ -515,9 +516,11 @@ EXPORT_SYMBOL_GPL(kunit_alloc_and_get_resource);
void kunit_remove_resource(struct kunit *test, struct kunit_resource *res)
{
- spin_lock(&test->lock);
+ unsigned long flags;
+
+ spin_lock_irqsave(&test->lock, flags);
list_del(&res->node);
- spin_unlock(&test->lock);
+ spin_unlock_irqrestore(&test->lock, flags);
kunit_put_resource(res);
}
EXPORT_SYMBOL_GPL(kunit_remove_resource);
@@ -597,6 +600,7 @@ EXPORT_SYMBOL_GPL(kunit_kfree);
void kunit_cleanup(struct kunit *test)
{
struct kunit_resource *res;
+ unsigned long flags;
/*
* test->resources is a stack - each allocation must be freed in the
@@ -608,9 +612,9 @@ void kunit_cleanup(struct kunit *test)
* protect against the current node being deleted, not the next.
*/
while (true) {
- spin_lock(&test->lock);
+ spin_lock_irqsave(&test->lock, flags);
if (list_empty(&test->resources)) {
- spin_unlock(&test->lock);
+ spin_unlock_irqrestore(&test->lock, flags);
break;
}
res = list_last_entry(&test->resources,
@@ -621,7 +625,7 @@ void kunit_cleanup(struct kunit *test)
* resource, and this can't happen if the test->lock
* is held.
*/
- spin_unlock(&test->lock);
+ spin_unlock_irqrestore(&test->lock, flags);
kunit_remove_resource(test, res);
}
#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
