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Mon, 23 Jun 2025 08:22:22 -0700 (PDT) Date: Mon, 23 Jun 2025 17:22:20 +0200 From: Petr Mladek To: Feng Tang Cc: Andrew Morton , Steven Rostedt , Lance Yang , Jonathan Corbet , linux-kernel@vger.kernel.org, paulmck@kernel.org, john.ogness@linutronix.de Subject: Re: [PATCH V2 5/5] panic: add note that panic_print interface is deprecated Message-ID: References: <20250616010840.38258-1-feng.tang@linux.alibaba.com> <20250616010840.38258-6-feng.tang@linux.alibaba.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: <20250616010840.38258-6-feng.tang@linux.alibaba.com> On Mon 2025-06-16 09:08:40, Feng Tang wrote: > Long term wise, the 'panic_sys_info' should be the only controlling > interface, which can be referred by other modules. Strictly speaking, 'panic_sys_info' is not a complete replacement for 'panic_print' because it does not allow replaying the log buffer during panic. I suggest to add a separate parameter "panic_console_replay" for the missing functionality first. And 'panic_print' will be obsoleted by both 'panic_sys_info' and 'panic_console_replay'. > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -76,6 +76,13 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list); > EXPORT_SYMBOL(panic_notifier_list); > > #ifdef CONFIG_SYSCTL > +static int sysctl_panic_print_handler(const struct ctl_table *table, int write, > + void *buffer, size_t *lenp, loff_t *ppos) > +{ > + printk_once("panic: 'panic_print' sysctl interface will be obsoleted by 'panic_sys_info' interface.\n"); > + return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); > +} > + > static const struct ctl_table kern_panic_table[] = { > #ifdef CONFIG_SMP > { > @@ -107,7 +114,7 @@ static const struct ctl_table kern_panic_table[] = { > .data = &panic_print, > .maxlen = sizeof(unsigned long), > .mode = 0644, > - .proc_handler = proc_doulongvec_minmax, > + .proc_handler = sysctl_panic_print_handler, This handles only the sysctl interface. We should do something similar also for the "panic_print" command line parameter. It would require using core_param_cb() instead of core_param(). > }, > { > .procname = "panic_on_warn", Best Regards, Petr