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authorJohn Ogness <john.ogness@linutronix.de>2023-01-12 17:18:13 +0106
committerPetr Mladek <pmladek@suse.com>2023-01-16 16:44:53 +0100
commit3ef5abd9b5c738bc6fa9a65e40331ef2cb03ad9c (patch)
tree304c478b077057aff9a335cf416483b187da2cab /kernel/printk/printk.c
parent5074ffbec67ac592614901771d3a15e1198d759d (diff)
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 6193bc90849a ("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: 6193bc90849a ("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
Diffstat (limited to 'kernel/printk/printk.c')
-rw-r--r--kernel/printk/printk.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 9ec101766471..3f7c8ed96512 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -123,6 +123,7 @@ bool console_srcu_read_lock_is_held(void)
{
return srcu_read_lock_held(&console_srcu);
}
+EXPORT_SYMBOL(console_srcu_read_lock_is_held);
#endif
enum devkmsg_log_bits {