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[24.6.192.50]) by smtp.gmail.com with ESMTPSA id k72-v6sm15734479pfj.63.2018.10.14.18.52.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 14 Oct 2018 18:52:22 -0700 (PDT) Subject: Re: [PATCH v3 13/18] of: overlay: check prevents multiple fragments touching same property To: Joe Perches , Rob Herring , Pantelis Antoniou , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Alan Tull , Moritz Fischer Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, devicetree@vger.kernel.org, linux-fpga@vger.kernel.org References: <1539563070-12969-1-git-send-email-frowand.list@gmail.com> <1539563070-12969-14-git-send-email-frowand.list@gmail.com> From: Frank Rowand Message-ID: <850f0866-1189-5a49-01c5-79caf270abbd@gmail.com> Date: Sun, 14 Oct 2018 18:52:21 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/14/18 18:06, Joe Perches wrote: > On Sun, 2018-10-14 at 17:24 -0700, frowand.list@gmail.com wrote: >> From: Frank Rowand >> >> Add test case of two fragments updating the same property. After >> adding the test case, the system hangs at end of boot, after >> after slub stack dumps from kfree() in crypto modprobe code. > [] >> -static int check_changeset_dup_add_node(struct overlay_changeset *ovcs) >> +static int changeset_dup_entry_check(struct overlay_changeset *ovcs) >> { >> - struct of_changeset_entry *ce_1, *ce_2; >> - char *fn_1, *fn_2; >> - int name_match; >> + struct of_changeset_entry *ce_1; >> + int dup_entry = 0; >> >> list_for_each_entry(ce_1, &ovcs->cset.entries, node) { >> - >> - if (ce_1->action == OF_RECONFIG_ATTACH_NODE || >> - ce_1->action == OF_RECONFIG_DETACH_NODE) { >> - >> - ce_2 = ce_1; >> - list_for_each_entry_continue(ce_2, &ovcs->cset.entries, node) { >> - if (ce_2->action == OF_RECONFIG_ATTACH_NODE || >> - ce_2->action == OF_RECONFIG_DETACH_NODE) { >> - /* inexpensive name compare */ >> - if (!of_node_cmp(ce_1->np->full_name, >> - ce_2->np->full_name)) { >> - /* expensive full path name compare */ >> - fn_1 = kasprintf(GFP_KERNEL, "%pOF", ce_1->np); >> - fn_2 = kasprintf(GFP_KERNEL, "%pOF", ce_2->np); >> - name_match = !strcmp(fn_1, fn_2); >> - kfree(fn_1); >> - kfree(fn_2); >> - if (name_match) { >> - pr_err("ERROR: multiple overlay fragments add and/or delete node %pOF\n", >> - ce_1->np); >> - return -EINVAL; >> - } >> - } >> - } >> - } >> - } >> + dup_entry |= find_dup_cset_node_entry(ovcs, ce_1); >> + dup_entry |= find_dup_cset_prop(ovcs, ce_1); > > I think this is worse performance than before. > > This now walks all entries when before it would > return -EINVAL directly when it found a match. Yes, it is worse performance, but that is OK. This is a check that is done when a devicetree overlay is applied. If an error occurs then that means that the overlay was incorrectly specified. The file drivers/of/unittest-data/overlay_bad_add_dup_prop.dts in this patch provides an example of how a bad overlay can be created. Once an error was detected, the check could return immediately, or it could continue to give a complete list of detected errors. I chose to give the complete list of detected errors. -Frank