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([2804:5078:9a0:f000:58f2:fc97:371f:2]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-89a35fb95d2sm3700951241.15.2025.09.05.11.30.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Sep 2025 11:30:54 -0700 (PDT) Message-ID: <85defbcb97090bcfa0995bbd58f8e41d8288ca44.camel@suse.com> Subject: Re: [PATCH v3 3/4] printk: nbcon: Allow KDB to acquire the NBCON context From: Marcos Paulo de Souza To: John Ogness , Greg Kroah-Hartman , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Jason Wessel , Daniel Thompson , Douglas Anderson Cc: linux-kernel@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net Date: Fri, 05 Sep 2025 15:30:48 -0300 In-Reply-To: <84y0qtdk99.fsf@jogness.linutronix.de> References: <20250902-nbcon-kgdboc-v3-0-cd30a8106f1c@suse.com> <20250902-nbcon-kgdboc-v3-3-cd30a8106f1c@suse.com> <84y0qtdk99.fsf@jogness.linutronix.de> Autocrypt: addr=mpdesouza@suse.com; prefer-encrypt=mutual; keydata=mDMEZ/0YqhYJKwYBBAHaRw8BAQdA4JZz0FED+JD5eKlhkNyjDrp6lAGmgR3LPTduPYGPT Km0Kk1hcmNvcyBQYXVsbyBkZSBTb3V6YSA8bXBkZXNvdXphQHN1c2UuY29tPoiTBBMWCgA7FiEE2g gC66iLbhUsCBoBemssEuRpLLUFAmf9GKoCGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk QemssEuRpLLWGxwD/S1I0bjp462FlKb81DikrOfWbeJ0FOJP44eRzmn20HmEBALBZIMrfIH2dJ5eM GO8seNG8sYiP6JfRjl7Hyqca6YsE Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (by Flathub.org) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-09-05 at 16:58 +0206, 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..352235a0eb4a484caccf86d3a > > 57d1a149218ecec 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, > > =C2=A0 * interrupted by the panic CPU while printing. > > =C2=A0 */ > > =C2=A0 if (other_cpu_in_panic() && > > + =C2=A0=C2=A0=C2=A0 READ_ONCE(kdb_printf_cpu) !=3D > > raw_smp_processor_id() && >=20 > This needs some sort of ifdef CONFIG_KGDB_KDB wrapped around it. > Maybe > it would be cleaner to have some macro. Ouch.. that's true! >=20 > #ifdef CONFIG_KGDB_KDB > #define KGDB_IS_ACTIVE() (READ_ONCE(kdb_printf_cpu) =3D=3D > raw_smp_processor_id()) > #else > #define KGDB_IS_ACTIVE() false > #endif >=20 > and then something like: >=20 > if (other_cpu_in_panic() && > =C2=A0=C2=A0=C2=A0 !KGDB_IS_ACTIVE() && > =C2=A0=C2=A0=C2=A0 (!is_reacquire || cur->unsafe_takeover)) { > return -EPERM; > } >=20 > Or however you prefer. We need to compile for !CONFIG_KGDB_KDB. I like the idea! Let me prepare it for v4. >=20 > John