linux/drivers/tty
Viresh Kumar b4d499241c tty: serial: bcm63xx: drop uart_port->lock before calling tty_flip_buffer_push()
The current driver triggers a lockdep warning for if tty_flip_buffer_push() is
called with uart_port->lock locked. This never shows up on UP kernels and comes
up only on SMP kernels.

Crash looks like this (produced with samsung.c driver):

-----
[<c0014d58>] (unwind_backtrace+0x0/0xf8) from [<c0011908>] (show_stack+0x10/0x14)
[<c0011908>] (show_stack+0x10/0x14) from [<c035da34>] (dump_stack+0x6c/0xac)
[<c035da34>] (dump_stack+0x6c/0xac) from [<c01b59ac>] (do_raw_spin_unlock+0xc4/0xd8)
[<c01b59ac>] (do_raw_spin_unlock+0xc4/0xd8) from [<c03627e4>] (_raw_spin_unlock_irqrestore+0xc/0)
[<c03627e4>] (_raw_spin_unlock_irqrestore+0xc/0x38) from [<c020a1a8>] (s3c24xx_serial_rx_chars+0)
[<c020a1a8>] (s3c24xx_serial_rx_chars+0x12c/0x260) from [<c020aae8>] (s3c64xx_serial_handle_irq+)
[<c020aae8>] (s3c64xx_serial_handle_irq+0x48/0x60) from [<c006aaa0>] (handle_irq_event_percpu+0x)
[<c006aaa0>] (handle_irq_event_percpu+0x50/0x194) from [<c006ac20>] (handle_irq_event+0x3c/0x5c)
[<c006ac20>] (handle_irq_event+0x3c/0x5c) from [<c006d864>] (handle_fasteoi_irq+0x80/0x13c)
[<c006d864>] (handle_fasteoi_irq+0x80/0x13c) from [<c006a4a4>] (generic_handle_irq+0x20/0x30)
[<c006a4a4>] (generic_handle_irq+0x20/0x30) from [<c000f454>] (handle_IRQ+0x38/0x94)
[<c000f454>] (handle_IRQ+0x38/0x94) from [<c0008538>] (gic_handle_irq+0x34/0x68)
[<c0008538>] (gic_handle_irq+0x34/0x68) from [<c00123c0>] (__irq_svc+0x40/0x70)
Exception stack(0xc04cdf70 to 0xc04cdfb8)
df60:                                     00000000 00000000 0000166e 00000000
df80: c04cc000 c050278f c050278f 00000001 c04d444c 410fc0f4 c03649b0 00000000
dfa0: 00000001 c04cdfb8 c000f758 c000f75c 60070013 ffffffff
[<c00123c0>] (__irq_svc+0x40/0x70) from [<c000f75c>] (arch_cpu_idle+0x28/0x30)
[<c000f75c>] (arch_cpu_idle+0x28/0x30) from [<c0054888>] (cpu_startup_entry+0x5c/0x148)
[<c0054888>] (cpu_startup_entry+0x5c/0x148) from [<c0497aa4>] (start_kernel+0x334/0x38c)
BUG: spinlock lockup suspected on CPU#0, kworker/0:1/360
 lock: s3c24xx_serial_ports+0x1d8/0x370, .magic: dead4ead, .owner: <none>/-1, .owner_cpu: -1
CPU: 0 PID: 360 Comm: kworker/0:1 Not tainted 3.11.0-rc6-next-20130819-00003-g75485f1 #2
Workqueue: events flush_to_ldisc
[<c0014d58>] (unwind_backtrace+0x0/0xf8) from [<c0011908>] (show_stack+0x10/0x14)
[<c0011908>] (show_stack+0x10/0x14) from [<c035da34>] (dump_stack+0x6c/0xac)
[<c035da34>] (dump_stack+0x6c/0xac) from [<c01b581c>] (do_raw_spin_lock+0x100/0x17c)
[<c01b581c>] (do_raw_spin_lock+0x100/0x17c) from [<c03628a0>] (_raw_spin_lock_irqsave+0x20/0x28)
[<c03628a0>] (_raw_spin_lock_irqsave+0x20/0x28) from [<c0203224>] (uart_start+0x18/0x34)
[<c0203224>] (uart_start+0x18/0x34) from [<c01ef890>] (__receive_buf+0x4b4/0x738)
[<c01ef890>] (__receive_buf+0x4b4/0x738) from [<c01efb44>] (n_tty_receive_buf2+0x30/0x98)
[<c01efb44>] (n_tty_receive_buf2+0x30/0x98) from [<c01f2ba8>] (flush_to_ldisc+0xec/0x138)
[<c01f2ba8>] (flush_to_ldisc+0xec/0x138) from [<c0031af0>] (process_one_work+0xfc/0x348)
[<c0031af0>] (process_one_work+0xfc/0x348) from [<c0032138>] (worker_thread+0x138/0x37c)
[<c0032138>] (worker_thread+0x138/0x37c) from [<c0037a7c>] (kthread+0xa4/0xb0)
[<c0037a7c>] (kthread+0xa4/0xb0) from [<c000e5f8>] (ret_from_fork+0x14/0x3c)
-----

Release the port lock before calling tty_flip_buffer_push() and reacquire it
after the call.

Similar stuff was already done for few other drivers in the past, like:

commit 2389b27216
Author: Thomas Gleixner <tglx@linutronix.de>
Date:   Tue May 29 21:53:50 2007 +0100

    [ARM] 4417/1: Serial: Fix AMBA drivers locking

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-08-27 16:17:34 -07:00
..
hvc tty/hvc_iucv: Disconnect IUCV connection when lowering DTR 2013-07-24 15:21:13 -07:00
ipwireless tty: ipwireless: Remove redundant NULL check before kfree 2013-03-15 13:58:32 -07:00
serial tty: serial: bcm63xx: drop uart_port->lock before calling tty_flip_buffer_push() 2013-08-27 16:17:34 -07:00
vt vt: make the default color configurable 2013-08-05 15:06:46 +08:00
amiserial.c TTY: amiserial, use module_platform_driver_probe() 2013-03-15 13:55:23 -07:00
bfin_jtag_comm.c TTY: switch tty_flip_buffer_push 2013-01-15 22:30:15 -08:00
cyclades.c TTY: add tty_port_tty_hangup helper 2013-03-18 16:24:29 -07:00
ehv_bytechan.c TTY: ehv_bytechan: add missing platform_driver_unregister() when module exit 2013-05-20 12:15:59 -07:00
goldfish.c goldfish: move to tty_port for flip buffers 2013-01-25 08:09:38 -08:00
isicom.c TTY: switch tty_flip_buffer_push 2013-01-15 22:30:15 -08:00
Kconfig tty: metag_da: Add metag DA TTY driver 2013-02-06 11:10:17 -08:00
Makefile tty: Add timed, writer-prioritized rw semaphore 2013-05-20 12:30:32 -07:00
metag_da.c tty: metag_da: avoid getting tty kref in dashtty_timer() 2013-02-06 11:10:17 -08:00
moxa.c TTY: add tty_port_tty_hangup helper 2013-03-18 16:24:29 -07:00
moxa.h
mxser.c tty: mxser: Fix build warning introduced by dfc7b837c7 (Re: linux-next: build warning after merge of the tty.current tree) 2013-05-22 10:26:02 -07:00
mxser.h
n_gsm.c Drivers: tty: n_gsm.c: fixed 7 errors & 6 warnings that checkpatch complained 2013-07-24 15:21:13 -07:00
n_hdlc.c
n_r3964.c
n_tracerouter.c
n_tracesink.c
n_tracesink.h
n_tty.c n_tty: Fix termios_rwsem lockdep false positive 2013-08-12 11:10:17 -07:00
nozomi.c TTY: add tty_port_tty_hangup helper 2013-03-18 16:24:29 -07:00
pty.c tty: Fix lock order in tty_do_resize() 2013-07-24 15:12:53 -07:00
rocket_int.h
rocket.c TTY: rocket, fix more no-PCI warnings 2013-05-20 12:15:59 -07:00
rocket.h
synclink_gt.c TTY: synclink_gt: fix DTR being raised on hang up 2013-04-12 14:08:17 -07:00
synclink.c TTY: synclink: replace bitmasks add operation with OR operation. 2013-07-29 12:47:37 -07:00
synclinkmp.c TTY: snyclinkmp: calculating wrong addresses 2013-07-24 15:23:38 -07:00
sysrq.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2013-07-04 15:35:08 -07:00
tty_audit.c audit: do not needlessly take a lock in tty_audit_exit 2013-04-30 15:31:28 -04:00
tty_buffer.c tty: Remove private constant from global namespace 2013-07-23 16:47:10 -07:00
tty_io.c tty: Only hangup once 2013-08-02 11:47:42 +08:00
tty_ioctl.c tty: Only guarantee termios read safety for throttle/unthrottle 2013-07-23 16:43:02 -07:00
tty_ldisc.c tty: Convert termios_mutex to termios_rwsem 2013-07-23 16:43:01 -07:00
tty_ldsem.c tty: Add timed, writer-prioritized rw semaphore 2013-05-20 12:30:32 -07:00
tty_mutex.c tty: tty_mutex.c: Fixed coding style warning (using printk) 2012-10-24 11:34:51 -07:00
tty_port.c tty_port: Fix refcounting leak in tty_port_tty_hangup() 2013-07-26 16:34:00 -07:00