From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-io1-f45.google.com (mail-io1-f45.google.com [209.85.166.45]) (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 8BBDE147C7D for ; Fri, 26 Apr 2024 13:40:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714138854; cv=none; b=q4I7ax3MNJP20rAz1XTc6cJH4pKrU/cD2Onh1VEOxkZKjn44Xy7aUhHdy5mjreP29MAG0IloVUHhwWZjRDo9fIQK8YbGMLy+A0ZkUtu1HEdq+nwBo6nWb+um9vejmcrvDJKSocOnUGgt/uppgxoNi2gJp7ulZSLG6ShE4FRlVW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714138854; c=relaxed/simple; bh=qSR9KdDtou4elM0dFMdXIBi+jhpmshH2TEdB7PPNUzY=; h=From:To:Cc:In-Reply-To:References:Subject:Message-Id:Date: MIME-Version:Content-Type; b=X/ETkDB5i1MCJmFW4zQF+lw+aIA6q1JMjFEP0EmUxowt77xC1+AI+7G8kT4eg1EssgqqQEbgo1B4LtLJ/etOzfIIKrljuR1NOcY2uozBig0MzKdkMgzU2dhg4B1QzXbLCKlGSXBBE85LbLJRJgZi0jTtt6YREnmXj5XuA4KGgR0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b=edkAi9YZ; arc=none smtp.client-ip=209.85.166.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b="edkAi9YZ" Received: by mail-io1-f45.google.com with SMTP id ca18e2360f4ac-7d9a64f140dso20168139f.1 for ; Fri, 26 Apr 2024 06:40:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1714138852; x=1714743652; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:date:message-id:subject :references:in-reply-to:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=+xyNmLTuWEvR72GEYCrL1zsIHBKSa0ehqFFEtMyryas=; b=edkAi9YZffOLOLGTJY1+vu0uEJ6hu+Ubudm0SeI8FWgRiYb0H7QBxEkNOe87Tz+NYI nOLI3UTrmKxU2sYPnU4tYzoA32axjVZPsb5HsMUre5n3cYPA6JlzQlSGKMfNxkSaC+q/ ZSt8uKUAFS8P/dWB+3NSCvz+HFIRD1eHAE7A1RQC3dddoYJwLmhQx/kiW0qiez7tCdLE Tx8SHF4t82W81E3Yppw0fdkHLggugAcILU8o8OhLJJvQQltjVe5TKPZjtSzxvWbkoK7u vADQg8opR2CwDHD+dhS02w8mv2L2uI1STlVfK1noTn8TY2f2AMS8YiPcUjBLEkHVclBp u8rA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1714138852; x=1714743652; h=content-transfer-encoding:mime-version:date:message-id:subject :references:in-reply-to:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=+xyNmLTuWEvR72GEYCrL1zsIHBKSa0ehqFFEtMyryas=; b=o6VtukuLY0mQfJfGbafVmuu0GBKCqWsBw55+fO0Jws43yDhE8dxJktdLFnNjqz3l/0 EvKVSKMyXYyNTtmdGgTdSu7GEmxMjYa2ZdXTnzaIz6tAxB8+joqiN+AhdEcSSJesFeyc 3FAJYT+YA/oS7USXxrsCKVMmFqfeUzFjdspnsIsRuSUMZJ1i1r+byemLixbHEyKI0fko 22nycayfGKORBHjdK6irZ9Kl947wfHVhuIrrqxSj15ruriwQDQBSg/6FTTG60lWNoGt1 ps1tWc5RV0hoXP/s3j8vk3Hp++e/sm8W4xFPZQ53OMEEwjD/BUr/ddJUhuyD/rqK1i0J 1ZZA== X-Forwarded-Encrypted: i=1; AJvYcCWVoW5IbN9eU31Qcx7qloHupfSz2a0nyqirRNT+NvW+3gFnPx0cTFjQ+k7S4p5hA0/mwdnys/lXI87w3Fjk541697Dnzwt3DUu7GROa X-Gm-Message-State: AOJu0Yw5CLmte0jQRRUDT1HMOLKxY5PK9vcS5nR6yJEF4s/BGWDhixJB 4Ms07lgbLlGKWylF7a9LSyV8iF3GMvdFRSOSNxBpB0Da20em+zfQFoKXghvP5iA= X-Google-Smtp-Source: AGHT+IF3mQB5HbulQg2CkJsEpbjz+y2/5fbhgBJ11VqFeOjJoS9ZZYtH/6hDcxbjMNxULlO5LHj3bw== X-Received: by 2002:a5d:8ac8:0:b0:7da:8d35:8a5e with SMTP id e8-20020a5d8ac8000000b007da8d358a5emr3331600iot.2.1714138852673; Fri, 26 Apr 2024 06:40:52 -0700 (PDT) Received: from [127.0.0.1] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id j13-20020a0566022ccd00b007dead4fd0efsm255275iow.18.2024.04.26.06.40.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Apr 2024 06:40:51 -0700 (PDT) From: Jens Axboe To: linke li Cc: xujianhao01@gmail.com, Andrew Morton , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: Subject: Re: [PATCH] sbitmap: use READ_ONCE to access map->word Message-Id: <171413885096.211722.564458609126458139.b4-ty@kernel.dk> Date: Fri, 26 Apr 2024 07:40:50 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Mailer: b4 0.12.5-dev-2aabd On Fri, 26 Apr 2024 18:34:44 +0800, linke li wrote: > In __sbitmap_queue_get_batch(), map->word is read several times, and > update atomically using atomic_long_try_cmpxchg(). But the first two read > of map->word is not protected. > > This patch moves the statement val = READ_ONCE(map->word) forward, > eliminating unprotected accesses to map->word within the function. > It is aimed at reducing the number of benign races reported by KCSAN in > order to focus future debugging effort on harmful races. > > [...] Applied, thanks! [1/1] sbitmap: use READ_ONCE to access map->word commit: 6ad0d7e0f4b68f87a98ea2b239123b7d865df86b Best regards, -- Jens Axboe