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6fad18fa51
linux/drivers/tty
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Rabin Vincent 6fad18fa51 serial: 8250: don't attempt a trylock if in sysrq 
Attempting to use SysRq via the 8250 serial port with spin lock
debugging on on a uniprocessor system results in the following splat:

 SysRq :
 BUG: spinlock trylock failure on UP on CPU#0, swapper/0
  lock: serial8250_ports+0x0/0x8c0, .magic: dead4ead, .owner: swapper/0, .owner_cpu: 0
 CPU: 0 PID: 0 Comm: swapper Not tainted 3.18.0-rc4+ #37
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
  ffffffff8245ba00 ffffffff81628b28 ffffffff812c8d27 ffffffff81628b48
  ffffffff8106812e ffffffff8245ba00 ffffffff814e22ed ffffffff81628b68
  ffffffff810681a6 0000000000000000 0000000000000000 ffffffff81628b88
 Call Trace:
  <IRQ>  [<ffffffff812c8d27>] dump_stack+0x19/0x1b
  [<ffffffff8106812e>] spin_dump+0x7e/0xd0
  [<ffffffff810681a6>] spin_bug+0x26/0x30
  [<ffffffff8106843c>] do_raw_spin_trylock+0x4c/0x60
  [<ffffffff812cdb1d>] _raw_spin_trylock+0x1d/0x60
  [<ffffffff812336d8>] serial8250_console_write+0x68/0x190
  [<ffffffff811eb0b0>] ? sprintf+0x40/0x50
  [<ffffffff8106ab5e>] call_console_drivers.constprop.11+0x9e/0xf0
  [<ffffffff8106b276>] console_unlock+0x3e6/0x490
  [<ffffffff8106b595>] vprintk_emit+0x275/0x530
  [<ffffffff812c869a>] printk+0x4d/0x4f
  [<ffffffff8121e612>] __handle_sysrq+0x62/0x1b0
  [<ffffffff8121e5b5>] ? __handle_sysrq+0x5/0x1b0
  [<ffffffff8121ebc6>] handle_sysrq+0x26/0x30
  [<ffffffff81233157>] serial8250_rx_chars+0x1d7/0x250
  [<ffffffff812338bb>] serial8250_handle_irq+0x7b/0x90
  [<ffffffff812338f3>] serial8250_default_handle_irq+0x23/0x30
  [<ffffffff812318b3>] serial8250_interrupt+0x63/0xe0
  [<ffffffff8106d80e>] handle_irq_event_percpu+0x4e/0x200
  [<ffffffff8106da01>] handle_irq_event+0x41/0x70
  [<ffffffff810701ee>] ? handle_edge_irq+0x1e/0x110
  [<ffffffff8107026e>] handle_edge_irq+0x9e/0x110
  [<ffffffff810041c2>] handle_irq+0x22/0x40
  [<ffffffff812d096e>] do_IRQ+0x4e/0xf0
  [<ffffffff812cf4ed>] common_interrupt+0x6d/0x6d
  <EOI>  [<ffffffff8100acbf>] ? default_idle+0x1f/0xd0
  [<ffffffff8100acbd>] ? default_idle+0x1d/0xd0
  [<ffffffff8100b61f>] arch_cpu_idle+0xf/0x20
  [<ffffffff8105c1db>] cpu_startup_entry+0x25b/0x360
  [<ffffffff812c726e>] rest_init+0xbe/0xd0
  [<ffffffff816a4dcb>] start_kernel+0x339/0x346
  [<ffffffff816a4495>] x86_64_start_reservations+0x2a/0x2c
  [<ffffffff816a4589>] x86_64_start_kernel+0xf2/0xf6
 HELP : loglevel(0-9) reboot(b) crash(c) show-all-locks(d) te...

Before ebade5e833 ("serial: 8250: Clean up the locking for -rt")
this was handled by not even attempting to try the lock if port->sysrq,
since it is known to be taken by the interrupt handler; see
https://bugzilla.kernel.org/show_bug.cgi?id=6716#c1.  Restore that
behavior.

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-25 17:06:40 -08:00
..
hvc tty: hvcs: Remove unnecessary KERN_ERR in hvcs.c 2014-11-05 19:24:07 -08:00
ipwireless tty: ipwireless: Fix probable mask then right shift defects 2014-11-05 20:06:33 -08:00
serial serial: 8250: don't attempt a trylock if in sysrq 2014-11-25 17:06:40 -08:00
vt tty: pr_warning->pr_warn and logging neatening 2014-11-25 17:06:38 -08:00
amiserial.c tty/amiserial: avoid interruptible_sleep_on 2014-01-07 17:05:21 -08:00
bfin_jtag_comm.c sched, cleanup, treewide: Remove set_current_state(TASK_RUNNING) after schedule() 2014-09-19 12:35:17 +02:00
cyclades.c tty: Remove tty_hung_up_p() tests from tty drivers' open() 2014-07-10 16:06:49 -07:00
ehv_bytechan.c tty: pr_warning->pr_warn and logging neatening 2014-11-25 17:06:38 -08:00
goldfish.c goldfish: off by one in goldfish_tty_console_setup() 2014-11-05 16:12:45 -08:00
isicom.c tty: pr_warning->pr_warn and logging neatening 2014-11-25 17:06:38 -08:00
Kconfig drivers/tty: ehv_bytechan fails to build as a module 2014-01-09 17:52:12 -06:00
Makefile tty: Add timed, writer-prioritized rw semaphore 2013-05-20 12:30:32 -07:00
metag_da.c tty/metag_da: Add console_poll module parameter 2014-09-28 21:35:56 -04:00
moxa.c TTY: fix decimal printf format specifiers prefixed with 0x 2014-09-08 15:51:35 -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 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-08-06 09:38:14 -07:00
n_hdlc.c drivers/tty/n_hdlc.c: replace kmalloc/memset by kzalloc 2014-05-28 13:33:18 -07:00
n_r3964.c tty: Always handle NULL flag ptr 2013-12-08 16:56:05 -08:00
n_tracerouter.c
n_tracesink.c
n_tracesink.h
n_tty.c Merge 3.18-rc4 into tty-next. 2014-11-10 12:42:04 +09:00
nozomi.c drivers/tty/nozomi.c: Use 'nozomi_setup_memory' instead of 'setup_memory' 2014-09-08 16:09:23 -07:00
pty.c pty, n_tty: Simplify input processing on final close 2014-11-05 18:50:42 -08:00
rocket_int.h
rocket.c tty: remove DEFINE_PCI_DEVICE_TABLE macro 2013-12-08 17:09:07 -08:00
rocket.h
synclink_gt.c synclink_gt: use pci_zalloc_consistent 2014-08-08 15:57:30 -07:00
synclink.c tty: Remove tty_hung_up_p() tests from tty drivers' open() 2014-07-10 16:06:49 -07:00
synclinkmp.c tty: Remove tty_hung_up_p() tests from tty drivers' open() 2014-07-10 16:06:49 -07:00
sysrq.c mm, oom: ensure memoryless node zonelist always includes zones 2014-08-06 18:01:21 -07:00
tty_audit.c audit: anchor all pid references in the initial pid namespace 2014-03-20 10:11:55 -04:00
tty_buffer.c tty: Flush ldisc buffer atomically with tty flip buffers 2014-11-05 18:50:43 -08:00
tty_io.c tty: warn on deprecated serial flags 2014-11-06 15:01:03 -08:00
tty_ioctl.c tty: Call methods in modern style 2014-11-05 20:18:30 -08:00
tty_ldisc.c tty: Allow safe access to termios for set_ldisc() handlers 2014-11-06 14:57:27 -08:00
tty_ldsem.c lockdep: Make held_lock->check and "int check" argument bool 2014-02-09 21:18:54 +01:00
tty_mutex.c tty: Preset lock subclass for nested tty locks 2014-11-05 18:50:42 -08:00
tty_port.c tty: Flush tty buffers after hardware shutdown 2014-11-06 14:57:27 -08:00