Re: [tip:locking/core] [futex] b78b0b6582: kselftests.damon.sysfs_memcg_path_leak.sh.fail

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Aug 07, 2026 at 07:49:27AM -0700, SJ Park wrote:

> > > kernel test robot noticed "kselftests.damon.sysfs_memcg_path_leak.sh.fail" on:
> > > 
> > > commit: b78b0b65825275f58336a43611a700de174be8c3 ("futex: Use runtime constants for __futex_hash() hot path")
> > > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git locking/core

> The test does a simple DAMON operation and runs kmemleak to see if it caused a
> leak.  It doesn't filter out leaks caused by something other than the DAMON
> operation, though.  So the test can fail even if there is a leak outside of
> DAMON.  This failure is the case.  I confirmed manual kmemleak run without any
> DAMON operation reports the leak on the kernel that was built with the reported
> commit [1] like below.

> So, the commit is not breaking DAMON.  But apparently it is leaking something.

Well, its doing a __init allocation and never freeing it because well,
futexes cannot be unloaded or anything.

Catalin, this seems rather daft, but what do I know. Is the below the
right way to tell it to STFU?

---
diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index ad917ff83854..afdbaf754fb7 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -45,6 +45,7 @@
 #include <linux/rseq.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/kmemleak.h>
 
 #include <vdso/futex.h>
 
@@ -2058,6 +2059,7 @@ static int __init futex_init(void)
 	order = get_order(size);
 
 	__futex_queues = kcalloc(nr_node_ids, sizeof(*__futex_queues), GFP_KERNEL);
+	kmemleak_not_leak(__futex_queues);
 
 	runtime_const_init(shift, __futex_shift);
 	runtime_const_init(mask,  __futex_mask);