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[192.55.52.136]) by mx.google.com with ESMTPS id x13si34693365pll.96.2019.04.11.07.59.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Apr 2019 07:59:15 -0700 (PDT) Received-SPF: pass (google.com: domain of keith.busch@intel.com designates 192.55.52.136 as permitted sender) client-ip=192.55.52.136; Authentication-Results: mx.google.com; spf=pass (google.com: domain of keith.busch@intel.com designates 192.55.52.136 as permitted sender) smtp.mailfrom=keith.busch@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Apr 2019 07:59:14 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,337,1549958400"; d="scan'208";a="163411880" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga001.fm.intel.com with ESMTP; 11 Apr 2019 07:59:14 -0700 Date: Thu, 11 Apr 2019 09:00:57 -0600 From: Keith Busch To: "Rafael J. Wysocki" Cc: Linux Kernel Mailing List , ACPI Devel Maling List , Linux Memory Management List , Dave Hansen , Dan Williams , Brice Goglin Subject: Re: [PATCH] hmat: Register attributes for memory hot add Message-ID: <20190411150057.GA7247@localhost.localdomain> References: <20190409214415.3722-1-keith.busch@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) 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, Apr 11, 2019 at 04:42:45PM +0200, Rafael J. Wysocki wrote: > On Tue, Apr 9, 2019 at 11:42 PM Keith Busch wrote: > > -static __init void hmat_register_targets(void) > > +static void hmat_register_targets(void) > > { > > struct memory_target *target; > > > > list_for_each_entry(target, &targets, node) { > > + if (!node_online(pxm_to_node(target->memory_pxm))) > > + continue; > > + > > hmat_register_target_initiators(target); > > hmat_register_target_perf(target); > > + target->registered = true; > > } > > } > > > > +static int hmat_callback(struct notifier_block *self, > > + unsigned long action, void *arg) > > +{ > > + struct memory_notify *mnb = arg; > > + int pxm, nid = mnb->status_change_nid; > > + struct memory_target *target; > > + > > + if (nid == NUMA_NO_NODE || action != MEM_ONLINE) > > + return NOTIFY_OK; > > + > > + pxm = node_to_pxm(nid); > > + target = find_mem_target(pxm); > > + if (!target || target->registered) > > + return NOTIFY_OK; > > + > > + hmat_register_target_initiators(target); > > + hmat_register_target_perf(target); > > + target->registered = true; > > + > > + return NOTIFY_OK; > > +} > > This appears to assume that there will never be any races between the > two functions above. > > It this guaranteed to be the case? The hmat_init() will call this directly before registering the memory notifier callback, so those two paths should be 'ok'. I may have assumed memory notification callbacks were single threaded, but after taking a quick look, I think I do need additional locking for this to be safe. I'll get that fixed up, thanks for the catch.