On Tue, 3 Sep 2024 20:48:53 -0400 "Liam R. Howlett" Liam.Howlett@oracle.com wrote:
- SeongJae Park sj@kernel.org [240903 20:45]:
damon_test_three_regions_in_vmas() initializes a maple tree with MM_MT_FLAGS. The flags contains MT_FLAGS_LOCK_EXTERN, which means mt_lock of the maple tree will not be used. And therefore the maple tree initialization code skips initialization of the mt_lock. However, __link_vmas(), which adds vmas for test to the maple tree, uses the mt_lock. In other words, the uninitialized spinlock is used. The problem becomes celar when spinlock debugging is turned on, since it reports spinlock bad magic bug. Fix the issue by not using the mt_lock as promised.
You can't do this, lockdep will tell you this is wrong.
Hmm, but lockdep was silence on my setup?
We need a lock and to use the lock for writes.
This code is executed by a single-thread test code. Do we still need the lock?
I'd suggest using different flags so the spinlock is used.
The reporter mentioned simply dropping MT_FLAGS_LOCK_EXTERN from the flags causes suspicious RCU usage message. May I ask if you have a suggestion of better flags?
Thanks, SJ
Reported-by: Guenter Roeck linux@roeck-us.net Closes: https://lore.kernel.org/1453b2b2-6119-4082-ad9e-f3c5239bf87e@roeck-us.net Fixes: d0cf3dd47f0d ("damon: convert __damon_va_three_regions to use the VMA iterator") Signed-off-by: SeongJae Park sj@kernel.org
mm/damon/tests/vaddr-kunit.h | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/mm/damon/tests/vaddr-kunit.h b/mm/damon/tests/vaddr-kunit.h index 83626483f82b..c6c7e0e0ab07 100644 --- a/mm/damon/tests/vaddr-kunit.h +++ b/mm/damon/tests/vaddr-kunit.h @@ -17,23 +17,19 @@ static int __link_vmas(struct maple_tree *mt, struct vm_area_struct *vmas, ssize_t nr_vmas) {
- int i, ret = -ENOMEM;
- int i; MA_STATE(mas, mt, 0, 0);
if (!nr_vmas) return 0;
- mas_lock(&mas); for (i = 0; i < nr_vmas; i++) { mas_set_range(&mas, vmas[i].vm_start, vmas[i].vm_end - 1); if (mas_store_gfp(&mas, &vmas[i], GFP_KERNEL))
goto failed;
return -ENOMEM;
- ret = 0;
-failed:
- mas_unlock(&mas);
- return ret;
- return 0;
} /* -- 2.39.2