From: Sergey Senozhatsky sergey.senozhatsky@gmail.com
commit 205d300aea75623e1ae4aa43e0d265ab9cf195fd upstream.
We have a number of "uart.port->desc.lock vs desc.lock->uart.port" lockdep reports coming from 8250 driver; this causes a bit of trouble to people, so let's fix it.
The problem is reverse lock order in two different call paths:
chain #1:
serial8250_do_startup() spin_lock_irqsave(&port->lock); disable_irq_nosync(port->irq); raw_spin_lock_irqsave(&desc->lock)
chain #2:
__report_bad_irq() raw_spin_lock_irqsave(&desc->lock) for_each_action_of_desc() printk() spin_lock_irqsave(&port->lock);
Fix this by changing the order of locks in serial8250_do_startup(): do disable_irq_nosync() first, which grabs desc->lock, and grab uart->port after that, so that chain #1 and chain #2 have same lock order.
Full lockdep splat:
====================================================== WARNING: possible circular locking dependency detected 5.4.39 #55 Not tainted ======================================================
swapper/0/0 is trying to acquire lock: ffffffffab65b6c0 (console_owner){-...}, at: console_lock_spinning_enable+0x31/0x57
but task is already holding lock: ffff88810a8e34c0 (&irq_desc_lock_class){-.-.}, at: __report_bad_irq+0x5b/0xba
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&irq_desc_lock_class){-.-.}: _raw_spin_lock_irqsave+0x61/0x8d __irq_get_desc_lock+0x65/0x89 __disable_irq_nosync+0x3b/0x93 serial8250_do_startup+0x451/0x75c uart_startup+0x1b4/0x2ff uart_port_activate+0x73/0xa0 tty_port_open+0xae/0x10a uart_open+0x1b/0x26 tty_open+0x24d/0x3a0 chrdev_open+0xd5/0x1cc do_dentry_open+0x299/0x3c8 path_openat+0x434/0x1100 do_filp_open+0x9b/0x10a do_sys_open+0x15f/0x3d7 kernel_init_freeable+0x157/0x1dd kernel_init+0xe/0x105 ret_from_fork+0x27/0x50
-> #1 (&port_lock_key){-.-.}: _raw_spin_lock_irqsave+0x61/0x8d serial8250_console_write+0xa7/0x2a0 console_unlock+0x3b7/0x528 vprintk_emit+0x111/0x17f printk+0x59/0x73 register_console+0x336/0x3a4 uart_add_one_port+0x51b/0x5be serial8250_register_8250_port+0x454/0x55e dw8250_probe+0x4dc/0x5b9 platform_drv_probe+0x67/0x8b really_probe+0x14a/0x422 driver_probe_device+0x66/0x130 device_driver_attach+0x42/0x5b __driver_attach+0xca/0x139 bus_for_each_dev+0x97/0xc9 bus_add_driver+0x12b/0x228 driver_register+0x64/0xed do_one_initcall+0x20c/0x4a6 do_initcall_level+0xb5/0xc5 do_basic_setup+0x4c/0x58 kernel_init_freeable+0x13f/0x1dd kernel_init+0xe/0x105 ret_from_fork+0x27/0x50
-> #0 (console_owner){-...}: __lock_acquire+0x118d/0x2714 lock_acquire+0x203/0x258 console_lock_spinning_enable+0x51/0x57 console_unlock+0x25d/0x528 vprintk_emit+0x111/0x17f printk+0x59/0x73 __report_bad_irq+0xa3/0xba note_interrupt+0x19a/0x1d6 handle_irq_event_percpu+0x57/0x79 handle_irq_event+0x36/0x55 handle_fasteoi_irq+0xc2/0x18a do_IRQ+0xb3/0x157 ret_from_intr+0x0/0x1d cpuidle_enter_state+0x12f/0x1fd cpuidle_enter+0x2e/0x3d do_idle+0x1ce/0x2ce cpu_startup_entry+0x1d/0x1f start_kernel+0x406/0x46a secondary_startup_64+0xa4/0xb0
other info that might help us debug this:
Chain exists of: console_owner --> &port_lock_key --> &irq_desc_lock_class
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&irq_desc_lock_class); lock(&port_lock_key); lock(&irq_desc_lock_class); lock(console_owner);
*** DEADLOCK ***
2 locks held by swapper/0/0: #0: ffff88810a8e34c0 (&irq_desc_lock_class){-.-.}, at: __report_bad_irq+0x5b/0xba #1: ffffffffab65b5c0 (console_lock){+.+.}, at: console_trylock_spinning+0x20/0x181
stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.39 #55 Hardware name: XXXXXX Call Trace: <IRQ> dump_stack+0xbf/0x133 ? print_circular_bug+0xd6/0xe9 check_noncircular+0x1b9/0x1c3 __lock_acquire+0x118d/0x2714 lock_acquire+0x203/0x258 ? console_lock_spinning_enable+0x31/0x57 console_lock_spinning_enable+0x51/0x57 ? console_lock_spinning_enable+0x31/0x57 console_unlock+0x25d/0x528 ? console_trylock+0x18/0x4e vprintk_emit+0x111/0x17f ? lock_acquire+0x203/0x258 printk+0x59/0x73 __report_bad_irq+0xa3/0xba note_interrupt+0x19a/0x1d6 handle_irq_event_percpu+0x57/0x79 handle_irq_event+0x36/0x55 handle_fasteoi_irq+0xc2/0x18a do_IRQ+0xb3/0x157 common_interrupt+0xf/0xf </IRQ>
Signed-off-by: Sergey Senozhatsky sergey.senozhatsky@gmail.com Fixes: 768aec0b5bcc ("serial: 8250: fix shared interrupts issues with SMP and RT kernels") Reported-by: Guenter Roeck linux@roeck-us.net Reported-by: Raul Rangel rrangel@google.com BugLink: https://bugs.chromium.org/p/chromium/issues/detail?id=1114800 Link: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDaf... Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Reviewed-by: Guenter Roeck linux@roeck-us.net Tested-by: Guenter Roeck linux@roeck-us.net Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/20200817022646.1484638-1-sergey.senozhatsky@gmail.... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/serial/8250/8250_port.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2198,6 +2198,10 @@ int serial8250_do_startup(struct uart_po
if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { unsigned char iir1; + + if (port->irqflags & IRQF_SHARED) + disable_irq_nosync(port->irq); + /* * Test for UARTs that do not reassert THRE when the * transmitter is idle and the interrupt has already @@ -2207,8 +2211,6 @@ int serial8250_do_startup(struct uart_po * allow register changes to become visible. */ spin_lock_irqsave(&port->lock, flags); - if (up->port.irqflags & IRQF_SHARED) - disable_irq_nosync(port->irq);
wait_for_xmitr(up, UART_LSR_THRE); serial_port_out_sync(port, UART_IER, UART_IER_THRI); @@ -2220,9 +2222,10 @@ int serial8250_do_startup(struct uart_po iir = serial_port_in(port, UART_IIR); serial_port_out(port, UART_IER, 0);
+ spin_unlock_irqrestore(&port->lock, flags); + if (port->irqflags & IRQF_SHARED) enable_irq(port->irq); - spin_unlock_irqrestore(&port->lock, flags);
/* * If the interrupt is not reasserted, or we otherwise