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Mon, 08 Sep 2025 08:23:07 -0700 (PDT) Date: Mon, 8 Sep 2025 17:23:05 +0200 From: Petr Mladek To: John Ogness Cc: Marcos Paulo de Souza , Greg Kroah-Hartman , Steven Rostedt , Sergey Senozhatsky , Jason Wessel , Daniel Thompson , Douglas Anderson , linux-kernel@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net Subject: Re: [PATCH v3 3/4] printk: nbcon: Allow KDB to acquire the NBCON context Message-ID: References: <20250902-nbcon-kgdboc-v3-0-cd30a8106f1c@suse.com> <20250902-nbcon-kgdboc-v3-3-cd30a8106f1c@suse.com> <84y0qtdk99.fsf@jogness.linutronix.de> 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: <84y0qtdk99.fsf@jogness.linutronix.de> On Fri 2025-09-05 16:58:34, John Ogness wrote: > On 2025-09-02, Marcos Paulo de Souza wrote: > > diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c > > index ff218e95a505fd10521c2c4dfb00ad5ec5773953..352235a0eb4a484caccf86d3a57d1a149218ecec 100644 > > --- a/kernel/printk/nbcon.c > > +++ b/kernel/printk/nbcon.c > > @@ -255,6 +258,7 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt, > > * interrupted by the panic CPU while printing. > > */ > > if (other_cpu_in_panic() && > > + READ_ONCE(kdb_printf_cpu) != raw_smp_processor_id() && > > This needs some sort of ifdef CONFIG_KGDB_KDB wrapped around it. Maybe > it would be cleaner to have some macro. Great catch! > #ifdef CONFIG_KGDB_KDB > #define KGDB_IS_ACTIVE() (READ_ONCE(kdb_printf_cpu) == raw_smp_processor_id()) > #else > #define KGDB_IS_ACTIVE() false > #endif I like this. It would fit into include/linux/kdb.h which already contains the #ifdef CONFIG_KGDB_KDB / #else / #endif sections. > and then something like: > > if (other_cpu_in_panic() && > !KGDB_IS_ACTIVE() && > (!is_reacquire || cur->unsafe_takeover)) { > return -EPERM; > } > > Or however you prefer. We need to compile for !CONFIG_KGDB_KDB. Best Regards, Petr