From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ABDC92F23; Wed, 2 Feb 2022 19:02:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1643828577; x=1675364577; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=M231Ao4yDTb4iZ/Nqoa87sdrwTCybShfUtJJRsYigEE=; b=lMR8Ljo+GdSNQUHWu1ryIC2RKtucAl/vSckgG1HJ+7XkYzseNoaagcJO 3/BDHpu5VU5XkgFqq8OgKJkSkVB3qqrvikrzjWt+YVgWQ/UUFkARwqOGa +ydBbQ9Tz42DBAn8doAMv+Ot8fzLRZsI9xdFIEesk8qiaWGtjNRFq9G84 tah+lJ6kAKqRmphGhU5fIFYE5Bzf05cTnrFiuR+u9S4AJRrckh97Jd1dL gYmvEBQ3uXyC2eFModLWQuoqOpHqAMmY97pBJz1KNbEMvw9Gd4lr+VJD6 rmOoE0Dx84954rsQY1zv/qaympe9UUo9mPoT/Y8cs2coPdUpsH1qwOJR7 A==; X-IronPort-AV: E=McAfee;i="6200,9189,10246"; a="235398633" X-IronPort-AV: E=Sophos;i="5.88,337,1635231600"; d="scan'208";a="235398633" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Feb 2022 11:02:56 -0800 X-IronPort-AV: E=Sophos;i="5.88,337,1635231600"; d="scan'208";a="523611584" Received: from svenur-mobl2.amr.corp.intel.com (HELO intel.com) ([10.252.133.34]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Feb 2022 11:02:56 -0800 Date: Wed, 2 Feb 2022 11:02:54 -0800 From: Ben Widawsky To: Dan Williams Cc: linux-cxl@vger.kernel.org, patches@lists.linux.dev, Alison Schofield , Ira Weiny , Jonathan Cameron , Vishal Verma , Bjorn Helgaas , Linux NVDIMM , Linux PCI Subject: Re: [PATCH v3 01/14] cxl/region: Add region creation ABI Message-ID: <20220202190254.gg3t5xhpdcnfpkp2@intel.com> References: <20220128002707.391076-1-ben.widawsky@intel.com> <20220128002707.391076-2-ben.widawsky@intel.com> <20220202182604.oangkxomx3npmobl@intel.com> <20220202182811.ivupsaeogyiwl5so@intel.com> <20220202184813.euepn3m2twpybpoc@intel.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On 22-02-02 11:00:04, Dan Williams wrote: > On Wed, Feb 2, 2022 at 10:48 AM Ben Widawsky wrote: > > > > On 22-02-02 10:28:11, Ben Widawsky wrote: > > > On 22-02-02 10:26:06, Ben Widawsky wrote: > > > > On 22-01-28 10:59:26, Dan Williams wrote: > > > > > On Fri, Jan 28, 2022 at 10:14 AM Dan Williams wrote: > > > > > [..] > > > > > > Here is that put_device() I was expecting, that kfree() earlier was a > > > > > > double-free it seems. > > > > > > > > > > > > Also, I would have expected a devm action to remove this. Something like: > > > > > > > > > > > > struct cxl_port *port = to_cxl_port(cxld->dev.parent); > > > > > > > > > > > > cxl_device_lock(&port->dev); > > > > > > if (port->dev.driver) > > > > > > devm_cxl_add_region(port->uport, cxld, id); > > > > > > > > I assume you mean devm_cxl_delete_region(), yes? > > > > > > > > > > else > > > > > > rc = -ENXIO; > > > > > > cxl_device_unlock(&port->dev); > > > > > > > > > > > > ...then no matter what you know the region will be unregistered when > > > > > > the root port goes away. > > > > > > > > > > ...actually, the lock and ->dev.driver check here are not needed > > > > > because this attribute is only registered while the cxl_acpi driver is > > > > > bound. So, it is safe to assume this is protected as decoder remove > > > > > synchronizes against active sysfs users. > > > > > > > > I'm somewhat confused when you say devm action to remove this. The current auto > > > > region deletion happens when the ->release() is called. Are you suggesting when > > > > the root decoder is removed I delete the regions at that point? > > > > > > Hmm. I went back and looked and I had changed this functionality at some > > > point... So forget I said that, it isn't how it's working currently. But the > > > question remains, are you suggesting I delete in the root decoder > > > unregistration? > > > > I think it's easier if I write what I think you mean.... Here are the relevant > > parts: > > > > devm_cxl_region_delete() is removed entirely. > > > > static void unregister_region(void *_cxlr) > > { > > struct cxl_region *cxlr = _cxlr; > > > > device_unregister(&cxlr->dev); > > } > > > > > > static int devm_cxl_region_add(struct cxl_decoder *cxld, struct cxl_region *cxlr) > > { > > struct cxl_port *port = to_cxl_port(cxld->dev.parent); > > struct device *dev = &cxlr->dev; > > int rc; > > > > rc = dev_set_name(dev, "region%d.%d:%d", port->id, cxld->id, cxlr->id); > > if (rc) > > return rc; > > > > rc = device_add(dev); > > if (rc) > > return rc; > > > > return devm_add_action_or_reset(&cxld->dev, unregister_region, cxlr); > > Decoders can't host devm actions. The host for this action would need > to be the parent port. Happy to change it since I can't imagine a decoder would go down without the port also going down. Can you please explain why a decoder can't host a devm action though. I'd like to understand that better. > > > } > > > > static ssize_t delete_region_store(struct device *dev, > > struct device_attribute *attr, > > const char *buf, size_t len) > > { > > struct cxl_decoder *cxld = to_cxl_decoder(dev); > > struct cxl_region *cxlr; > > > > cxlr = cxl_find_region_by_name(cxld, buf); > > if (IS_ERR(cxlr)) > > return PTR_ERR(cxlr); > > > > devm_release_action(dev, unregister_region, cxlr); > > Yes, modulo the same comment as before that the decoder object is not > a suitable devm host. This also needs a solution for the race between > these 2 actions: > > echo "ACPI0017:00" > /sys/bus/platform/drivers/cxl_acpi/unbind > echo $region > /sys/bus/cxl/devices/$decoder/delete_region Is there a better solution than taking the root port lock?