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From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Jason Wessel <jason.wessel@windriver.com>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Douglas Anderson <dianders@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jirislaby@kernel.org>,
	kgdb-bugreport@lists.sourceforge.net,
	linux-serial@vger.kernel.org
Subject: [PATCH printk v3 37/40] tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console()
Date: Mon,  7 Nov 2022 15:22:35 +0106	[thread overview]
Message-ID: <20221107141638.3790965-38-john.ogness@linutronix.de> (raw)
In-Reply-To: <20221107141638.3790965-1-john.ogness@linutronix.de>

Calling tty_find_polling_driver() can lead to uart_set_options() being
called (via the poll_init() callback of tty_operations) to configure the
uart. But uart_set_options() can also be called by register_console()
(via the setup() callback of console).

Take the console_list_lock to synchronize against register_console() and
also use it for console list traversal. This also ensures the console list
cannot change until the polling console has been chosen.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 drivers/tty/serial/kgdboc.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 82b4b4d67823..8c2b7ccdfebf 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -189,12 +189,20 @@ static int configure_kgdboc(void)
 	if (kgdboc_register_kbd(&cptr))
 		goto do_register;
 
+	/*
+	 * tty_find_polling_driver() can call uart_set_options()
+	 * (via poll_init) to configure the uart. Take the console_list_lock
+	 * in order to synchronize against register_console(), which can also
+	 * configure the uart via uart_set_options(). This also allows safe
+	 * traversal of the console list.
+	 */
+	console_list_lock();
+
 	p = tty_find_polling_driver(cptr, &tty_line);
-	if (!p)
+	if (!p) {
+		console_list_unlock();
 		goto noconfig;
-
-	/* For safe traversal of the console list. */
-	console_list_lock();
+	}
 
 	/*
 	 * Take console_lock to serialize device() callback with
-- 
2.30.2


  parent reply	other threads:[~2022-11-07 14:19 UTC|newest]

Thread overview: 103+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-07 14:15 [PATCH printk v3 00/40] reduce console_lock scope John Ogness
2022-11-07 14:15 ` [PATCH printk v3 01/40] rcu: implement lockdep_rcu_enabled for !CONFIG_DEBUG_LOCK_ALLOC John Ogness
2022-11-07 18:01   ` Paul E. McKenney
2022-11-07 19:23     ` John Ogness
2022-11-08 19:27       ` Paul E. McKenney
2022-11-09 17:49         ` Paul E. McKenney
2022-11-08 10:29   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 02/40] serial: kgdboc: Lock console list in probe function John Ogness
2022-11-09  8:20   ` Daniel Thompson
2022-11-07 14:16 ` [PATCH printk v3 03/40] printk: Convert console_drivers list to hlist John Ogness
2022-11-07 14:16 ` [PATCH printk v3 04/40] printk: Prepare for SRCU console list protection John Ogness
2022-11-08 12:14   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 05/40] printk: fix setting first seq for consoles John Ogness
2022-11-08 12:20   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 06/40] um: kmsg_dump: only dump when no output console available John Ogness
2022-11-08 12:41   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 07/40] console: introduce console_is_enabled() wrapper John Ogness
2022-11-08 16:18   ` Petr Mladek
2022-11-10 15:05     ` John Ogness
2022-11-11 13:32       ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 08/40] printk: use console_is_enabled() John Ogness
2022-11-08 17:40   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 09/40] um: kmsg_dump: " John Ogness
2022-11-09 14:52   ` Petr Mladek
2022-11-09 14:56   ` Petr Mladek
2022-11-09 14:57     ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 10/40] kdb: kdb_io: " John Ogness
2022-11-09  8:22   ` Daniel Thompson
2022-11-09 14:59   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 11/40] um: kmsg_dumper: use srcu console list iterator John Ogness
2022-11-09 15:05   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 12/40] tty: serial: kgdboc: document console_lock usage John Ogness
2022-11-09  8:23   ` Daniel Thompson
2022-11-09 15:19   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 13/40] tty: tty_io: " John Ogness
2022-11-09 15:20   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 14/40] proc: consoles: " John Ogness
2022-11-09 15:22   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 15/40] kdb: use srcu console list iterator John Ogness
2022-11-09  8:53   ` Daniel Thompson
2022-11-09  9:27     ` John Ogness
2022-11-09 15:27       ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 16/40] printk: console_flush_all: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 17/40] printk: console_unblank: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 18/40] printk: console_flush_on_panic: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 19/40] printk: console_device: " John Ogness
2022-11-09 15:58   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 20/40] printk: __pr_flush: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 21/40] printk: introduce console_list_lock John Ogness
2022-11-10 12:58   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 22/40] console: introduce console_is_registered() John Ogness
2022-11-10 13:00   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 23/40] serial_core: replace uart_console_enabled() with uart_console_registered() John Ogness
2022-11-08  8:46   ` Geert Uytterhoeven
2022-11-10 13:24     ` Petr Mladek
2022-11-10 13:46       ` John Ogness
2022-11-07 14:16 ` [PATCH printk v3 24/40] tty: nfcon: use console_is_registered() John Ogness
2022-11-08  8:39   ` Geert Uytterhoeven
2022-11-10 13:58   ` Petr Mladek
2022-11-10 14:19     ` John Ogness
2022-11-10 17:50       ` Eero Tamminen
2022-11-07 14:16 ` [PATCH printk v3 25/40] efi: earlycon: " John Ogness
2022-11-10 14:28   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 26/40] tty: hvc: " John Ogness
2022-11-10 14:52   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 27/40] tty: serial: earlycon: " John Ogness
2022-11-10 15:00   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 28/40] tty: serial: pic32_uart: " John Ogness
2022-11-10 15:01   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 29/40] tty: serial: samsung_tty: " John Ogness
2022-11-10 15:01   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 30/40] tty: serial: xilinx_uartps: " John Ogness
2022-11-10 15:04   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 31/40] usb: early: xhci-dbc: " John Ogness
2022-11-10 15:05   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 32/40] netconsole: avoid CON_ENABLED misuse to track registration John Ogness
2022-11-10 15:17   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 33/40] printk, xen: fbfront: create/use safe function for forcing preferred John Ogness
2022-11-10 15:34   ` Petr Mladek
2022-11-10 16:03     ` John Ogness
2022-11-10 17:26       ` Petr Mladek
2022-11-10 22:37         ` John Ogness
2022-11-11 10:48   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 34/40] tty: tty_io: use console_list_lock for list synchronization John Ogness
2022-11-07 14:16 ` [PATCH printk v3 35/40] proc: consoles: use console_list_lock for list iteration John Ogness
2022-11-07 14:16 ` [PATCH printk v3 36/40] tty: serial: kgdboc: use console_list_lock for list traversal John Ogness
2022-11-09  9:06   ` Daniel Thompson
2022-11-09  9:44     ` John Ogness
2022-11-10 18:00       ` Petr Mladek
2022-11-07 14:16 ` John Ogness [this message]
2022-11-10 15:13   ` [PATCH printk v3 37/40] tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() Daniel Thompson
2022-11-10 18:03   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 38/40] tty: serial: kgdboc: use console_list_lock to trap exit John Ogness
2022-11-10 15:18   ` Daniel Thompson
2022-11-11  9:59   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 39/40] printk: relieve console_lock of list synchronization duties John Ogness
2022-11-07 16:30   ` John Ogness
2022-11-11 10:27     ` Petr Mladek
2022-11-11 13:06   ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 40/40] tty: serial: sh-sci: use setup() callback for early console John Ogness
2022-11-08  8:53   ` Geert Uytterhoeven
2022-11-11 17:15   ` Petr Mladek
2022-11-11 14:43 ` [PATCH printk v3 00/40] reduce console_lock scope Mathieu Desnoyers

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