From nobody Thu Apr 2 09:21:54 2026 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 766F32264D6 for ; Mon, 30 Mar 2026 01:33:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774834394; cv=none; b=PmBrrW17wWd0guz4pUCbM40FuW8P3pXmQsNU4sXTYTjo8fov+uY/G+68a2U1ZlTOZneu5HaQn2+iBERlz2KokRNvneBgdKdmsQwcsuSaQMBb1V7YWUGxolrk+ClJMl+YP+ThMf+aWmg6SsZ8qnT+841Hgp4DIdTVvCvrhDtU4E4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774834394; c=relaxed/simple; bh=o10lYr/d/TbLmFjFNSNP03sAxAADk/D1nuRcpZkVhvQ=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=PxSNhoQECD3J8B5FWnTA3MA2RW6/MQPUIjN24K9enMriMj5T7gXUCgT6vsytD56j0eMMnmDp/JCMQTJX1eY4TYlEEHvCUTdoAOg7sWqOrONkpEW4jioOloJQNTRLCM7Ep4tHigslMwqTtOq4aGtiR1udBVqO4FNq8GV8xWMhGdY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 63610e9a2bd811f1aa26b74ffac11d73-20260330 X-CID-CACHE: Type:Local,Time:202603300930+08,HitQuantity:1 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.12,REQID:9aa8da55-1bf2-4400-91f0-30bcba024ea9,IP:0,U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:0 X-CID-META: VersionHash:e7bac3a,CLOUDID:c48a2a661bf133fb5ebece269e41cca1,BulkI D:nil,BulkQuantity:0,Recheck:0,SF:102|850|898,TC:nil,Content:0|15|50,EDM:- 3,IP:nil,URL:0,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,A V:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: 63610e9a2bd811f1aa26b74ffac11d73-20260330 Received: from localhost [(10.44.16.150)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 232600819; Mon, 30 Mar 2026 09:33:00 +0800 From: Yu Peng To: Peter Zijlstra Cc: Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , linux-kernel@vger.kernel.org, Yu Peng Subject: [PATCH] locking/osq_lock: Use READ_ONCE() for node->prev Date: Mon, 30 Mar 2026 09:32:55 +0800 Message-Id: <20260330013255.25937-1-pengyu@kylinos.cn> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" osq_lock() consults node->prev in the vcpu_is_preempted() heuristic while a concurrent predecessor may update it via WRITE_ONCE(next->prev, prev) during unqueue. This read only affects the decision to abort optimistic spinning; stale values do not affect queue linkage or lock correctness. Use READ_ONCE() to mark the shared read and match the concurrent WRITE_ONCE() update. No functional change intended. Signed-off-by: Yu Peng --- kernel/locking/osq_lock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c index b4233dc2c2b04..db4545e7bb72c 100644 --- a/kernel/locking/osq_lock.c +++ b/kernel/locking/osq_lock.c @@ -144,7 +144,7 @@ bool osq_lock(struct optimistic_spin_queue *lock) * polling, be careful. */ if (smp_cond_load_relaxed(&node->locked, VAL || need_resched() || - vcpu_is_preempted(node_cpu(node->prev)))) + vcpu_is_preempted(node_cpu(READ_ONCE(node->prev))))) return true; =20 /* unqueue */ --=20 2.43.0