Re: [PATCH 2/3] futex: Use RCU-based per-CPU reference counting instead of rcuref_t

[Sebastian Andrzej Siewior]

On 2025-07-07 16:36:22 [+0200], To linux-kernel@xxxxxxxxxxxxxxx wrote:
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> 
> The use of rcuref_t for reference counting introduces a performance bottleneck
> when accessed concurrently by multiple threads during futex operations.

just folded this bit after kernel test robot complained:

diff --git a/include/linux/futex.h b/include/linux/futex.h
index cd773febd497b..9e9750f049805 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -113,7 +113,7 @@ static inline int futex_hash_allocate_default(void)
 	return 0;
 }
 static inline int futex_hash_free(struct mm_struct *mm) { return 0; }
-static inline void futex_mm_init(struct mm_struct *mm) { }
+static inline int futex_mm_init(struct mm_struct *mm) { return 0; }
 
 #endif
 

Sebastian