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Mon, 12 Jan 2026 07:03:32 -0800 (PST) Date: Mon, 12 Jan 2026 16:03:30 +0100 From: Petr Mladek To: Gal Pressman Cc: Feng Tang , Andrew Morton , linux-kernel@vger.kernel.org, Mark Bloch , Nimrod Oren Subject: Re: [PATCH] panic: only warn about deprecated panic_print on write access Message-ID: References: <20260106163321.83586-1-gal@nvidia.com> <0107a066-72bb-4632-9129-70dab0707316@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon 2026-01-12 08:48:37, Gal Pressman wrote: > On 12/01/2026 5:32, Feng Tang wrote: > > On Sun, Jan 11, 2026 at 10:28:55AM +0200, Gal Pressman wrote: > >> On 08/01/2026 17:52, Petr Mladek wrote: > >>> On Wed 2026-01-07 15:20:44, Feng Tang wrote: > >>>> On Wed, Jan 07, 2026 at 08:41:22AM +0200, Gal Pressman wrote: > >>>>> On 07/01/2026 5:00, Feng Tang wrote: > >>>>>>> @@ -1014,7 +1015,6 @@ static int panic_print_set(const char *val, const struct kernel_param *kp) > >>>>>>> > >>>>>>> static int panic_print_get(char *val, const struct kernel_param *kp) > >>>>>>> { > >>>>>>> - panic_print_deprecated(); > >>>>>> > >>>>>> Actually this was intentional, in one of the patch version, this > >>>>>> panic_print_get() was not there but reusing the param_get_ulong(). > >>>>>> > >>>>>> It was added later as sometimes developer do want to runtime check > >>>>>> the current 'panic_print' setting through /sys/module/kernel/parameters/ > >>>>>> interface, and I thought it may be better to give the warning. > >>>>> > >>>>> I figured it would make sense to keep the behaviors consistent. > >>> > >>> I see. > >>> > >>>> When people run 'sysctl -a', in 99.9% cases, the users don't care > >>>> 'panic_print' or even don't know what 'panic_print' is, that's why > >>>> I think removing it makes sense. > >>>> > >>>> But for a user running 'cat /sys/module/kernel/parameters/panic_rint', > >>>> giving a warning is meaningful. > >>> > >>> Makes perfect sense. > >>> > >>> We need to make people aware that "panic_print" will eventually go > >>> away. 'sysctl -a' is different because it prints all values and > >>> there is big chance that the caller is not interested in "panic_print" > >>> at all. > >>> > >>> It makes sense to remove the warning from sysctl read. But I would > >>> keep it in sysfs read. > >> > >> The sysfs entry exhibits the same issue, just different command: > >> > >> # systool -m kernel -v > >> > >> Or: > >> > >> # grep . /sys/module/kernel/parameters/* I see. > > Yes, when user checks the kernel parameters, I think it's better to > > give them a notice (it's a pr_info_once(), which only prints once > > for the whole power cycle). > This log message causes a lot of noise for people who have no idea what > panic_print is. > We started seeing this print internally, and it took a long time and > significant resources to figure out what changed and if we were doing > anything wrong in our environments. > > Seeing a deprecation notice is alarming, especially if you don't know > what is being deprecated or how it affects you. In my opinion, we > shouldn't print this unless someone actually uses panic_print. I am fine with printing the warning only when the value is modified (set/write). Best Regards, Petr PS: Sigh, it is hard to change or remove an interface. It is always better to think twice before introducing one.