From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06106C433F5 for ; Tue, 23 Nov 2021 03:33:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7955B6B0071; Mon, 22 Nov 2021 22:32:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 71E196B0072; Mon, 22 Nov 2021 22:32:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5BDDF6B0073; Mon, 22 Nov 2021 22:32:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0245.hostedemail.com [216.40.44.245]) by kanga.kvack.org (Postfix) with ESMTP id 47B856B0071 for ; Mon, 22 Nov 2021 22:32:46 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 0D61682DAC for ; Tue, 23 Nov 2021 03:32:36 +0000 (UTC) X-FDA: 78838772712.13.61D2C30 Received: from mail-lf1-f41.google.com (mail-lf1-f41.google.com [209.85.167.41]) by imf05.hostedemail.com (Postfix) with ESMTP id ADC4650932DA for ; Tue, 23 Nov 2021 03:32:30 +0000 (UTC) Received: by mail-lf1-f41.google.com with SMTP id k37so87597210lfv.3 for ; Mon, 22 Nov 2021 19:32:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1cS+AGoyo0T1C4anWdwhsoIk52AyuDzpTpUnOg/pvp8=; b=P2gurxCO8YQs+0wFw2RyLDFXFTltWYvIe+GUqg+7As4lv9/oBpIUdt5ScnDzQWFplG xBewWWzpZG51MLBTQG9Z7fiBHggGWPkht2/yH67fAg/ZDlpMnQdqG7+sjndKPdEUlHDj zq2EA3OR7HijngAb9e+ZPVHDzYD87iltA0/tJkzfmY6jMEvQeS8G2YKxrZvEFxkF43Dn iSTmVEtmGhPbZAsvUd0DMw5ZuIgwXR81n7r0kqeXAGotD2QGkX+VllchkDpdO+6ogwu3 u+2R7NYZlseTK5SDFZdp3NKzfmh68xzR/vCKekeLRG/h28yInwePz/9CbcxbbssG3taL 75MA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1cS+AGoyo0T1C4anWdwhsoIk52AyuDzpTpUnOg/pvp8=; b=1+V0JVWlXGTZYGA+sOs2meeHEIq2HZmMlUb/biBU6f7Xjfciadd3GeT1TRcv8hjjhe nqc6PBgn9suNsCNPyCYHtitwGS3PFK4CR4LmiwssxIhvd6F8FLILtKS9KptqZVZuMcXF tvdXg0f2X1r4wQLuhWgQ+XVWe7azTxr4sZNL1XAtDaEpdlZTiLJ0xz4ZG41CsBgWFbyg X5h92ef4oXdvzaog9lWHuhqu14uhl1SyzrIa2XnwVz8xLoo3FkmstaMoqPRcgMd2PM4y iMIPqwM2PSaqCCMJVaAm4cV3+UrwJqozHObeirSbiL2sc/r/JvHtdfvCt2PFzU9yS8oQ t10Q== X-Gm-Message-State: AOAM531rcUTbTBjcGLj2gC/apqUimIr4457jrETHtLm4wlaLLw3EjVZt IRzEKpaM9NTVGuLjpqgCTbtixWPsCQG/MYSio88= X-Google-Smtp-Source: ABdhPJwGzHFRGdxPATCev+5g1UgtmYO2kWOdzRsoltdw2Hy1iq9PNo2F1zOfviji9xyUHRfxmQWxIy8A8aDvUgz+KTM= X-Received: by 2002:a05:6512:138f:: with SMTP id p15mr1458070lfa.648.1637638354052; Mon, 22 Nov 2021 19:32:34 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Wonhyuk Yang Date: Tue, 23 Nov 2021 12:32:25 +0900 Message-ID: Subject: Re: [Question] The necessity of transaction ID in SLUB. To: Christoph Lameter Cc: linux-mm@kvack.org, Joonsoo Kim Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: ADC4650932DA X-Stat-Signature: k1tukronnes7cja9d51qq1smzdbrbmgr Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=P2gurxCO; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf05.hostedemail.com: domain of vvghjk1234@gmail.com designates 209.85.167.41 as permitted sender) smtp.mailfrom=vvghjk1234@gmail.com X-HE-Tag: 1637638350-297127 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001196, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 22, 2021 at 6:25 PM Christoph Lameter wrote: > > > 1) c->cpu_slab->page is unfrozen and frozen by another cpu. (is it possible?) > > Yes. > > > In the first case, cpu_slab structure can be different. But updating > > freelist isn't a problem. > > It is a problem because the update can occur on a different processor > without the TID which can race with another update on another processor. > Do you mean that without TID, multiple cpu can race on one cpu_slab->freelist? How is it possible? As you know, cpu_slab is per-cpu variable and cpu_slab->freelist is accessed via "this_cpu_cmpxchg" in the area where preemption is enabled. I can't imagine what kind of situation will make that race happen.