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([2600:1700:2442:6db0:b5d7:d916:de6d:55a0]) by smtp.gmail.com with ESMTPSA id p21-20020a9d6955000000b0063b31e8f457sm4140337oto.75.2022.09.11.23.45.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 11 Sep 2022 23:45:41 -0700 (PDT) Message-ID: <3fcea82c-f5cf-f066-67b9-08669c44a9c6@gmail.com> Date: Mon, 12 Sep 2022 01:45:40 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH] driver: of: overlay: demote message to warning Content-Language: en-US From: Frank Rowand To: Daniel Walker Cc: Pantelis Antoniou , Rob Herring , xe-linux-external@cisco.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220907230709.271889-1-danielwa@cisco.com> <973f7127-8165-45f6-071f-04360046b7d7@gmail.com> <20220908003510.GE4320@zorba> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/8/22 12:55, Frank Rowand wrote: > On 9/7/22 19:35, Daniel Walker wrote: >> On Wed, Sep 07, 2022 at 06:54:02PM -0500, Frank Rowand wrote: >>> On 9/7/22 18:07, Daniel Walker wrote: >>>> This warning message shows by default on the vast majority of overlays >>>> applied. Despite the text identifying this as a warning it is marked >>>> with the loglevel for error. At Cisco we filter the loglevels to only >>>> show error messages. We end up seeing this message but it's not really >>>> an error. >>>> >>>> For this reason it makes sense to demote the message to the warning >>>> loglevel. >>>> >>>> Cc: xe-linux-external@cisco.com >>>> Signed-off-by: Daniel Walker >>>> --- >>>> drivers/of/overlay.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c >>>> index bd8ff4df723d..4ae276ed9a65 100644 >>>> --- a/drivers/of/overlay.c >>>> +++ b/drivers/of/overlay.c >>>> @@ -358,7 +358,7 @@ static int add_changeset_property(struct overlay_changeset *ovcs, >>>> } >>>> >>>> if (!of_node_check_flag(target->np, OF_OVERLAY)) >>>> - pr_err("WARNING: memory leak will occur if overlay removed, property: %pOF/%s\n", >>>> + pr_warn("WARNING: memory leak will occur if overlay removed, property: %pOF/%s\n", >>>> target->np, new_prop->name); >>>> >>>> if (ret) { >>> >>> NACK >>> >>> This is showing a real problem with the overlay. >> >> What's the real problem ? >> >> Daniel > > A memory leak when the overlay is removed. > > I'll send a patch to update the overlay file in Documumentation/devicetree/ to provide > more information about this. If you don't see a patch by tomorrow, feel free to > ping me. > > -Frank The good news is that your question prodded me to start improving the in kernel documentation of overlays. The promised patch is a rough start at: https://lore.kernel.org/all/20220912062615.3727029-1-frowand.list@gmail.com/ The bad news is that what I wrote doesn't explain the memory leak in any more detail. If an overlay adds a property to a node in the base device tree then the memory allocated to do the add will not be freed when the overlay is removed. Since it is possible to add and remove overlays multiple times, the ensuing size of the memory leak is potentially unbounded. -Frank