John Ogness 3ef5abd9b5 tty: serial: kgdboc: fix mutex locking order for configure_kgdboc() ... Several mutexes are taken while setting up console serial ports. In particular, the tty_port->mutex and @console_mutex are taken: serial_pnp_probe serial8250_register_8250_port uart_add_one_port (locks tty_port->mutex) uart_configure_port register_console (locks @console_mutex) In order to synchronize kgdb's tty_find_polling_driver() with register_console(), commit 6193bc9084 ("tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console()") takes the @console_mutex. However, this leads to the following call chain (with locking): platform_probe kgdboc_probe configure_kgdboc (locks @console_mutex) tty_find_polling_driver uart_poll_init (locks tty_port->mutex) uart_set_options This is clearly deadlock potential due to the reverse lock ordering. Since uart_set_options() requires holding @console_mutex in order to serialize early initialization of the serial-console lock, take the @console_mutex in uart_poll_init() instead of configure_kgdboc(). Since configure_kgdboc() was using @console_mutex for safe traversal of the console list, change it to use the SRCU iterator instead. Add comments to uart_set_options() kerneldoc mentioning that it requires holding @console_mutex (aka the console_list_lock). Fixes: 6193bc9084 ("tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console()") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> [pmladek@suse.com: Export console_srcu_read_lock_is_held() to fix build kgdboc as a module.] Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230112161213.1434854-1-john.ogness@linutronix.de		2023-01-16 16:44:53 +01:00
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braille.c	printk: Replace strncmp() with str_has_prefix()	2019-08-16 09:54:08 +02:00
braille.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
console_cmdline.h	printk: Fix preferred console selection with multiple matches	2020-02-18 09:34:42 +01:00
index.c	printk: avoid -Wsometimes-uninitialized warning	2021-10-04 10:28:43 +02:00
internal.h	Revert "printk: Wait for the global console lock when the system is going down"	2022-06-23 18:41:40 +02:00
Makefile	printk: move printk sysctl to printk/sysctl.c	2022-01-22 08:33:35 +02:00
printk_ringbuffer.c	printk: ringbuffer: Improve prb_next_seq() performance	2022-01-26 16:00:32 +01:00
printk_ringbuffer.h	printk: ringbuffer: Improve prb_next_seq() performance	2022-01-26 16:00:32 +01:00
printk_safe.c	Revert "printk: Wait for the global console lock when the system is going down"	2022-06-23 18:41:40 +02:00
printk.c	tty: serial: kgdboc: fix mutex locking order for configure_kgdboc()	2023-01-16 16:44:53 +01:00
sysctl.c	printk: Fix incorrect __user type in proc_dointvec_minmax_sysadmin()	2022-02-03 11:27:38 -08:00