From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f13.google.com (mail-pj2-f13.google.com [74.125.227.141]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 517254EE86D for ; Mon, 5 Oct 2026 17:16:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.141 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791220619; cv=none; b=X2pNuxYFulYH3rEIrYOptHmqC299R+7NzSjB3B97S1SP91TuKSPc5J3Tmp2ZZZEPxpqzDSzfi3hDdkyKGLgVm7zAEJCYoBduOJ/ne7KL+Qjmha65oUz82GbYOMtEDRxXVQ0/kMqkh91y0cQwqxYAiKmBvkZbsJV5hEzZA2RHT2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791220619; c=relaxed/simple; bh=9wEbN2n5LQFaWEnfgc/fjcdj12CgL82mEepIN/jxNKo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YNhlsfxs9+xK+8QT5g/hyDwHlmGpjKpPGMjGMOrjSksWVFqM0Calwkf6+1X8hqbwGho+/8Cq6LvcEEOwUNAja8Kv42gxqwLw5WPwwziA8AhRpUkxsZFyMopbLipAHZoSz91dbvkia9By75UA+4WGB5pham1SDOR8eLZbCkuzrIQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=QbL07d6a; arc=none smtp.client-ip=74.125.227.141 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QbL07d6a" Received: by mail-pj2-f13.google.com with SMTP id 98e67ed59e1d1-396ccb65437so1070426a91.3 for ; Mon, 05 Oct 2026 10:16:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791220617; x=1791825417; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=InVY38nfxVAqb/WmgYkdpIBcCwx01OQ8UJwYgwWPio4=; b=QbL07d6azUEZP/YgXxJwnZHrBE7Emtw9fZ9uAoWdNta0PxzGeVEH9cdyBwnP0kM6nW NhPhFcVGXVi52g3tTCcTgvhZjgV1scowezYg8/MdHe0QydTs66hR7bIQ3mcWDtioq6Ht wTtjOohdhBnmATxJJ9ny3J4xzb99AGqW5DWp3WCVnfPpBA4HA7iFFwm3QPM+szpCRkX+ nD6oV1fLhYLz9h5rYwwucbcvd/170kFqdeK6Fd1y76IoE7fWWWeNnZA5ZfwiJZ5Mvm9D 1Vwe6lJLcknwrDexGy2Na0LwWbqW6sRuVQ+Fwb+fEt/50MEDUSNtU0kiGCLKteSvHbMS 64LQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791220617; x=1791825417; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=InVY38nfxVAqb/WmgYkdpIBcCwx01OQ8UJwYgwWPio4=; b=et3dt9yTl4kN0hBeWyclJWOdd0o43IpRTHddGHtd58kArfr6CKMLkPIgaA9ClQGjEB U2sEZwHma7CJOS8X7JatxojuEsnOECB8qEXaj298MLFV/vmG9u+lkrG/SmU//efIQBfR dDkwAJRwdxtoCaiVEO17rIlmtR32kaCWKUGYxXNEgfM8SAQ4Qlop4ykGC19ceyO/JGXd UtHtn5D9vLcf93L1G+be8HhKk5TMBQ4uHhWK0aPZYZ64f7QcT0yaWq01ljvH+t4dvxQU Hq1yEVRlT6Bt4DpuRaNKbMDrG4fvrjGoIje3tMi/YKh3Gz+q4hw5aPg1r+7xT3UHMnGv rfFA== X-Forwarded-Encrypted: i=1; AKwUvBwDEqtIPMOTMTLZZmuVGhljRiuzrDr202sEre05o3dCDBsAZLLuuDmDiq2IfWgggz3ZqFaNFKqILBoOpUY=@vger.kernel.org X-Gm-Message-State: AFq9FYKOu6fRJZ7tE6QyEa8+k4RilGyv43NSmjLtVNImEFLUaVnI6RzV va0FoJb1h9XTLC+WVK83EKPzGQWAf4NOLuWbkNN8OQVBLD6Q9LVht9f9 X-Gm-Gg: AYBFou0HIbcNwCCzC/JaMkHPwacBkDAXEILOZuiNuRlF/QFk4rpx9CiVyyOTx98b/Wx QW7yI5pIpUJVjVNl0y2USqqQOSWW1SopWSmYDU8FG1wVlKTDDkabZEl5OBPslv51N4eye3Tke3p 9+KSGJRThEknJ2GwOLbTPG3lfZheWeBMqq4amgA81ZdmHg+LG/RpwPfHCVFSAIrsiL3eifRSmxx WpspxNl9eVv9WwOgqFI2EnfZ1TbC9k+ZpCfz9EDnCAorN4WzVmDdtrgpN6DdNbmRwyBezO4ihOG iNq/EsHQhkPmR6z508Nd/3DGFc6+rYdA4RtliYnPaiyKPANz1BQGWnwPKwFsOBq4QqIqcN378TL hpXbiRQ/jSNGIYXTIPl1omiONfkZOUcrVMF71RSPWLk94epvaCg+xitbIEAYH/22B5Mzm9PCQHc vH3jrgs+hgmaSUw+pD/Ql/aYv9EgtBJQELwBmYfL6rrzSeZ66DwyI8y7SsqwsBuA0VuqlG/QsOB 2EM4QPai22iQ0qzTh/mE5GBGxHxJg== X-Received: by 2002:a17:90b:3e85:b0:3a7:8350:3f7e with SMTP id 98e67ed59e1d1-3a783504695mr5636453a91.44.1791220616043; Mon, 05 Oct 2026 10:16:56 -0700 (PDT) Received: from kernel.tail6741c6.ts.net ([216.195.201.24]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a853cafddesm406910a91.10.2026.10.05.10.16.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Oct 2026 10:16:55 -0700 (PDT) From: Kunwu Chan To: paulmck@kernel.org, corbet@lwn.net, mingo@redhat.com, frederic@kernel.org, neeraj.upadhyay@kernel.org, josh@joshtriplett.org, urezki@gmail.com, dave@stgolabs.net, lianux.mm@gmail.com Cc: stern@rowland.harvard.edu, parri.andrea@gmail.com, will@kernel.org, peterz@infradead.org, boqun@kernel.org, npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com, dlustig@nvidia.com, joelagnelf@nvidia.com, skhan@linuxfoundation.org, rdunlap@infradead.org, longman@redhat.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, kunwu.chan@gmail.com, brads@mainlining.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, lkmm@lists.linux.dev, linux-doc@vger.kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH RFC v3 05/15] hazptr: add debug option to force the acquire slow path Date: Tue, 6 Oct 2026 01:15:19 +0800 Message-ID: <20261005171529.1378809-6-kunwu.chan@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261005171529.1378809-1-kunwu.chan@gmail.com> References: <20261005171529.1378809-1-kunwu.chan@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a debug option that makes hazptr_acquire() always enter __hazptr_acquire(), even when a per-CPU slot is available. This allows the slow path, including its lock acquisition, to be exercised by lockdep-heavy workloads. It also lets hazptrtorture exercise the slow path without requiring the per-CPU slots to be exhausted. Suggested-by: Boqun Feng Signed-off-by: Kunwu Chan --- include/linux/hazptr.h | 3 ++- kernel/rcu/Kconfig.debug | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/linux/hazptr.h b/include/linux/hazptr.h index 275cbe54b075..4ee02d23abc9 100644 --- a/include/linux/hazptr.h +++ b/include/linux/hazptr.h @@ -245,7 +245,8 @@ void *hazptr_acquire(struct hazptr_ctx *ctx, void * const *addr_p) ctx->acquire_cpu = smp_processor_id(); ctx->acquire_caller = _THIS_IP_; #endif - if (unlikely(slot->addr)) + if (IS_ENABLED(CONFIG_HAZPTR_ACQUIRE_FORCE_SLOWPATH) || + unlikely(slot->addr)) return __hazptr_acquire(ctx, addr_p); WRITE_ONCE(slot->addr, READ_ONCE(hazptr_wildcard)); /* Store B */ diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug index 7c3c6017b266..3a2e9d7f58f8 100644 --- a/kernel/rcu/Kconfig.debug +++ b/kernel/rcu/Kconfig.debug @@ -265,4 +265,14 @@ config HAZPTR_DEBUG Say Y here if you want to enable those assert, N otherwise. +config HAZPTR_ACQUIRE_FORCE_SLOWPATH + bool "Force hazard-pointer acquire into the slow path" + depends on DEBUG_KERNEL + default n + help + Make hazptr_acquire() always enter __hazptr_acquire(). + This is useful for testing slow-path locking, especially + with lockdep. It also lets hazptrtorture exercise the slow + path without filling the per-CPU slots. + endmenu # "RCU Debugging" -- 2.43.0