locking fix

GIT PULL Merged Ingo Molnar 2 participants 2 messages Nov 8, 2025 Futex

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Ingo Molnar

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2025-11-08 13:04 UTC #0 lore raw

Linus,

Please pull the latest locking/urgent Git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-2025-11-08

# HEAD: 4cb5ac2626b5704ed712ac1d46b9d89fdfc12c5d futex: Optimize per-cpu reference counting

Fix (well, cut in half) a futex performance regression on PowerPC.

Thanks,

Ingo

------------------>
Peter Zijlstra (1):
futex: Optimize per-cpu reference counting

 kernel/futex/core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

kernel/futex/core.c +6 -6

index 125804fbb5cb..2e77a6e5c865 100644
@@ -1680,10 +1680,10 @@ static bool futex_ref_get(struct futex_private_hash *fph)
 {
 	struct mm_struct *mm = fph->mm;
 
-	guard(rcu)();
+	guard(preempt)();
 
-	if (smp_load_acquire(&fph->state) == FR_PERCPU) {
-		this_cpu_inc(*mm->futex_ref);
+	if (READ_ONCE(fph->state) == FR_PERCPU) {
+		__this_cpu_inc(*mm->futex_ref);
 		return true;
 	}

@@ -1694,10 +1694,10 @@ static bool futex_ref_put(struct futex_private_hash *fph)
 {
 	struct mm_struct *mm = fph->mm;
 
-	guard(rcu)();
+	guard(preempt)();
 
-	if (smp_load_acquire(&fph->state) == FR_PERCPU) {
-		this_cpu_dec(*mm->futex_ref);
+	if (READ_ONCE(fph->state) == FR_PERCPU) {
+		__this_cpu_dec(*mm->futex_ref);
 		return false;
 	}

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merge bot Merged

2025-11-08 17:15 UTC #1 lore raw

The pull request you sent on Sat, 8 Nov 2025 14:04:18 +0100:

Quoted 1 line

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-2025-11-08

has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/e6f55fe790a698aba6f98bf6ae4f1c04246c5040

Thank you!

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