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Thu, 29 Oct 2026 00:20:05 -0700 (PDT) Received: from localhost ([116.86.153.182]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae6e7ac878sm2842003a91.4.2026.10.29.00.20.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 00:20:04 -0700 (PDT) Date: Thu, 29 Oct 2026 15:19:59 +0800 From: Chris Down To: Petr Mladek Cc: John Ogness , Sergey Senozhatsky , Steven Rostedt , Marcos Paulo de Souza , Naveen Kumar Chaudhary , linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 14/16] printk: Do not set Braille console as preferred_console Message-ID: References: <20260929120546.328616-1-pmladek@suse.com> <20260929120546.328616-15-pmladek@suse.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260929120546.328616-15-pmladek@suse.com> User-Agent: Mutt/2.3.3 (9073d26d) (2026-06-12) Petr Mladek writes: >- if (brl_options) >+ if (is_new_entry) >+ INIT_LIST_HEAD(&pc->preferred_dev_node); is_new_entry is derived from pc->name[0]/pc->devname[0] being empty, and console_setup() can store an empty name: console=,115200 console=tty1 The first one creates an entry with name "" (and links it). The second one stops the lookup loop at the same slot, sees it as new again, and re-initialises a node which is still linked, followed by list_add(). With DEBUG_LIST + BUG_ON_DATA_CORRUPTION: list_add corruption. next->prev should be prev (ffffb010209fc0c0), but was ffffb01023cd1fa0. (next=ffffb01023cd1fa0). kernel BUG at lib/list_debug.c:29! Call trace: __list_add_valid_or_report+0xbc/0x1c0 (P) add_or_update_preferred_console+0x6fc/0x9c0 __add_preferred_console+0x11c/0x160 console_setup+0x2e4/0x348 obsolete_checksetup+0x148/0x190 unknown_bootoption+0x150/0x328 parse_one+0x108/0x480 parse_args+0x158/0x3d0 start_kernel+0x134/0x488 "console=,foo:bar" does the same on the first console= when SPCR added an entry, since it matches the SPCR slot via the empty devname (see 7/16). Rejecting empty name/devname in add_or_update_preferred_console() (see my comment on 7/16) should fix that. >- preferred_dev_console = i; >+ if (!list_empty(&pc->preferred_dev_node)) >+ list_del_init(&pc->preferred_dev_node); >+ } else if (!is_braille_console_preferred(pc)) { >+ if (list_empty(&pc->preferred_dev_node)) >+ list_add(&pc->preferred_dev_node, &preferred_dev_console); >+ else >+ list_move(&pc->preferred_dev_node, &preferred_dev_console); list_del_init() and list_move() are both fine on an initialised self-linked node (list_move() passes the DEBUG_LIST checks in __list_del_entry_valid()), so the list_empty() checks can go. With these fixed: Acked-by: Chris Down Thanks!