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 0F4FDECAAD3 for ; Thu, 1 Sep 2022 14:48:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9195B8D000C; Thu, 1 Sep 2022 10:48:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8C8D18D0006; Thu, 1 Sep 2022 10:48:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 769068D000C; Thu, 1 Sep 2022 10:48:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 66A6E8D0006 for ; Thu, 1 Sep 2022 10:48:15 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 3B8C4AB464 for ; Thu, 1 Sep 2022 14:48:15 +0000 (UTC) X-FDA: 79863796950.28.F06C872 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf08.hostedemail.com (Postfix) with ESMTP id D9207160059 for ; Thu, 1 Sep 2022 14:48:14 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EC7C161DD3; Thu, 1 Sep 2022 14:48:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DDEAC433D6; Thu, 1 Sep 2022 14:48:08 +0000 (UTC) Date: Thu, 1 Sep 2022 10:48:39 -0400 From: Steven Rostedt To: Kent Overstreet Cc: Peter Zijlstra , Suren Baghdasaryan , akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, void@manifault.com, juri.lelli@redhat.com, ldufour@linux.ibm.com, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, changbin.du@intel.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, arnd@arndb.de, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-mm@kvack.org, iommu@lists.linux.dev, kasan-dev@googlegroups.com, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 03/30] Lazy percpu counters Message-ID: <20220901104839.5691e1c9@gandalf.local.home> In-Reply-To: <20220901143219.n7jg7cbp47agqnwn@moria.home.lan> References: <20220830214919.53220-1-surenb@google.com> <20220830214919.53220-4-surenb@google.com> <20220901143219.n7jg7cbp47agqnwn@moria.home.lan> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662043694; a=rsa-sha256; cv=none; b=NPDZIaB3CpjH7ghn9KV1IWUH4NUqVb4jigX34+mqt5okIaoPNON2wlKyOclZb1ZJs2Z3gF 4G712jcGBv+S47CpaZG/J8pSi1Zt+3K/Djwf2Y8p2vxGZB3prkROfLQv6ErajMGaouGyH2 ywOAhYlqBEtHzNNSK8FLZKkA2cWm73E= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf08.hostedemail.com: domain of "SRS0=hZ//=ZE=goodmis.org=rostedt@kernel.org" designates 139.178.84.217 as permitted sender) smtp.mailfrom="SRS0=hZ//=ZE=goodmis.org=rostedt@kernel.org" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662043694; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Jf8cO2t6hUZhUrp3a7pSCi1cULdqUuGpU01vQQWB5m4=; b=v3vSedpb9Qwx+um4RtXvGwCAv50XZUhcyQUiJNWHNdrzcZaMXZdBzl4HFA/EuVZ+DpZzSP nZnPLO+Xo90MOB/7IedYk0gOEIPCjv9MMYHOQny3rZLpAl42thB4agMYYXyC8fHl5LCCgl QJJ57v2sNjwyvBhtfvJMJ9h6G/AK2RM= X-Rspamd-Server: rspam09 Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf08.hostedemail.com: domain of "SRS0=hZ//=ZE=goodmis.org=rostedt@kernel.org" designates 139.178.84.217 as permitted sender) smtp.mailfrom="SRS0=hZ//=ZE=goodmis.org=rostedt@kernel.org" X-Rspam-User: X-Stat-Signature: p43o15xpw4rhhaih9ii1nudkkoghnnpt X-Rspamd-Queue-Id: D9207160059 X-HE-Tag: 1662043694-61082 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 1 Sep 2022 10:32:19 -0400 Kent Overstreet wrote: > On Thu, Sep 01, 2022 at 08:51:31AM +0200, Peter Zijlstra wrote: > > On Tue, Aug 30, 2022 at 02:48:52PM -0700, Suren Baghdasaryan wrote: > > > +static void lazy_percpu_counter_switch_to_pcpu(struct raw_lazy_percpu_counter *c) > > > +{ > > > + u64 __percpu *pcpu_v = alloc_percpu_gfp(u64, GFP_ATOMIC|__GFP_NOWARN); > > > > Realize that this is incorrect when used under a raw_spinlock_t. > > Can you elaborate? All allocations (including GFP_ATOMIC) grab normal spin_locks. When PREEMPT_RT is configured, normal spin_locks turn into a mutex, where as raw_spinlock's do not. Thus, if this is done within a raw_spinlock with PREEMPT_RT configured, it can cause a schedule while holding a spinlock. -- Steve