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author | John Ogness <john.ogness@linutronix.de> | 2023-01-12 17:12:13 +0100 |
---|---|---|
committer | Petr Mladek <pmladek@suse.com> | 2023-01-16 16:44:53 +0100 |
commit | 3ef5abd9b5c738bc6fa9a65e40331ef2cb03ad9c (patch) | |
tree | 304c478b077057aff9a335cf416483b187da2cab /kernel/printk | |
parent | printk: htmldocs: add missing description (diff) | |
download | linux-3ef5abd9b5c738bc6fa9a65e40331ef2cb03ad9c.tar.xz linux-3ef5abd9b5c738bc6fa9a65e40331ef2cb03ad9c.zip |
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')
-rw-r--r-- | kernel/printk/printk.c | 1 |
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 { |