Hi Johan,
Am 2014-04-23 17:15, schrieb Johan Hedberg:
On Wed, Apr 16, 2014, Andreas Bießmann wrote:
This patch fixes a recursive locking scenario when using BCSP
connection via
8250 driver. The 8250 driver may tty_wakeup() in interrupt context
which
results in hci_uart_tx_wakeup(). This in turn will call uart_write()
in the
very same context and therefore will spin_lock() the same lock within
the
same context.
Here is the call stack:
---8<---
=============================================
[ INFO: possible recursive locking detected ]
3.4.87-gf1a3cc3 #3 Tainted: G O
---------------------------------------------
swapper/0 is trying to acquire lock:
(&port_lock_key){-.-...}, at: [<c023e21c>] uart_write+0x60/0xfc
but task is already holding lock:
(&port_lock_key){-.-...}, at: [<c0242830>]
serial8250_handle_irq+0x24/0x88
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&port_lock_key);
lock(&port_lock_key);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by swapper/0:
#0: (&(&i->lock)->rlock){-.-...}, at: [<c0240f44>]
serial8250_interrupt+0x2c/0xc0
#1: (&port_lock_key){-.-...}, at: [<c0242830>]
serial8250_handle_irq+0x24/0x88
stack backtrace:
[<c0014234>] (unwind_backtrace+0x0/0xec) from [<c0398448>]
(dump_stack+0x20/0x24)
[<c0398448>] (dump_stack+0x20/0x24) from [<c006eebc>]
(print_deadlock_bug+0xb4/0xe4)
[<c006eebc>] (print_deadlock_bug+0xb4/0xe4) from [<c006f04c>]
(check_deadlock.isra.20+0x160/0x18c)
[<c006f04c>] (check_deadlock.isra.20+0x160/0x18c) from [<c0070890>]
(validate_chain.isra.24+0x4a4/0x4f0)
[<c0070890>] (validate_chain.isra.24+0x4a4/0x4f0) from [<c00715a0>]
(__lock_acquire+0x670/0x740)
[<c00715a0>] (__lock_acquire+0x670/0x740) from [<c0071cb0>]
(lock_acquire+0x138/0x15c)
[<c0071cb0>] (lock_acquire+0x138/0x15c) from [<c03a5904>]
(_raw_spin_lock_irqsave+0x54/0x68)
[<c03a5904>] (_raw_spin_lock_irqsave+0x54/0x68) from [<c023e21c>]
(uart_write+0x60/0xfc)
[<c023e21c>] (uart_write+0x60/0xfc) from [<bf0716d8>]
(hci_uart_tx_wakeup+0x9c/0x160 [hci_uart])
[<bf0716d8>] (hci_uart_tx_wakeup+0x9c/0x160 [hci_uart]) from
[<bf0717f4>] (hci_uart_tty_wakeup+0x58/0x5c [hci_uart])
[<bf0717f4>] (hci_uart_tty_wakeup+0x58/0x5c [hci_uart]) from
[<c02246ec>] (tty_wakeup+0x48/0x68)
[<c02246ec>] (tty_wakeup+0x48/0x68) from [<c023efb0>]
(uart_write_wakeup+0x2c/0x30)
[<c023efb0>] (uart_write_wakeup+0x2c/0x30) from [<c0241d0c>]
(serial8250_tx_chars+0xf0/0x140)
[<c0241d0c>] (serial8250_tx_chars+0xf0/0x140) from [<c0242878>]
(serial8250_handle_irq+0x6c/0x88)
[<c0242878>] (serial8250_handle_irq+0x6c/0x88) from [<c02428c4>]
(serial8250_default_handle_irq+0x30/0x34)
[<c02428c4>] (serial8250_default_handle_irq+0x30/0x34) from
[<c0240f5c>] (serial8250_interrupt+0x44/0xc0)
[<c0240f5c>] (serial8250_interrupt+0x44/0xc0) from [<c0087c70>]
(handle_irq_event_percpu+0xc4/0x2cc)
[<c0087c70>] (handle_irq_event_percpu+0xc4/0x2cc) from [<c0087ec4>]
(handle_irq_event+0x4c/0x6c)
[<c0087ec4>] (handle_irq_event+0x4c/0x6c) from [<c008a368>]
(handle_edge_irq+0x114/0x14c)
[<c008a368>] (handle_edge_irq+0x114/0x14c) from [<c0087528>]
(generic_handle_irq+0x40/0x54)
[<c0087528>] (generic_handle_irq+0x40/0x54) from [<c01f1900>]
(gpio_irq_handler+0x168/0x1ac)
[<c01f1900>] (gpio_irq_handler+0x168/0x1ac) from [<c0087528>]
(generic_handle_irq+0x40/0x54)
[<c0087528>] (generic_handle_irq+0x40/0x54) from [<c000ed7c>]
(handle_IRQ+0x70/0x94)
[<c000ed7c>] (handle_IRQ+0x70/0x94) from [<c000877c>]
(omap3_intc_handle_irq+0x64/0x78)
[<c000877c>] (omap3_intc_handle_irq+0x64/0x78) from [<c000df44>]
(__irq_svc+0x44/0x78)
--->8---
Signed-off-by: Andreas Bießmann <andreas@xxxxxxxxxxxx>
Cc: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Cc: Gustavo Padovan <gustavo@xxxxxxxxxxx>
Cc: Johan Hedberg <johan.hedberg@xxxxxxxxx>
Cc: linux-bluetooth@xxxxxxxxxxxxxxx
---
It seems at least one other guy had the very same problem with another
uart
(mpc52xx): http://www.spinics.net/lists/linux-rt-users/msg09246.html
I wonder, if my approach is right. It is runtime tested with 3.4.87 on
our
board and work around the mentioned recursive locking. But I do not
know, if
it should be fixed in another way.
If it is right, I'd work some more on it to get the fix mainline.
drivers/bluetooth/hci_ldisc.c | 49
++++++++++++++++++++++++++++++++++++-----
drivers/bluetooth/hci_uart.h | 2 ++
2 files changed, 45 insertions(+), 6 deletions(-)
This seems to be tackling the same problem as the following patch from
Felipe Balbi (of which a new revision was sent earlier today):
Subject: [PATCH 02/13] bluetooth: hci_ldisc: fix deadlock condition
seems so, thanks for the pointer!
Best regards
Andreas Bießmann
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