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
..
8250_accent.c
8250_acorn.c	tty: remove use of __devexit	2012-11-21 15:27:46 -08:00
8250_boca.c
8250_core.c	serial: 8250: don't attempt a trylock if in sysrq	2014-11-25 17:06:40 -08:00
8250_dma.c	serial: 8250_dma: no need to set tx_err twice	2014-11-06 15:01:03 -08:00
8250_dw.c	serial: 8250_dw: Use 64-bit access for OCTEON.	2014-11-25 17:06:39 -08:00
8250_early.c	tty/serial: fix 8250 early console option passing to regular console	2014-06-19 13:07:26 -07:00
8250_em.c	serial: 8250_em: Remove out-of-memory message	2014-11-05 20:18:30 -08:00
8250_exar_st16c554.c
8250_fintek.c	8250/fintek: Use rs485 handler from serial_core	2014-11-06 14:59:21 -08:00
8250_fourport.c
8250_fsl.c	serial: 8250: introduce up_to_u8250p() helper	2014-07-17 18:16:23 -07:00
8250_gsc.c	parisc: Fix interrupt routing for C8000 serial ports	2013-07-31 23:42:32 +02:00
8250_hp300.c	serial: hp300: Remove obsolete comments	2014-11-05 20:18:30 -08:00
8250_hub6.c
8250_mtk.c	tty: serial: Fix mediatek UART driver setting baudrate issue	2014-11-06 14:57:25 -08:00
8250_omap.c	tty: serial: 8250: omap: line is unsigned, don't check < 0	2014-11-25 17:06:38 -08:00
8250_pci.c	serial: Fix io address assign flow with Fintek PCI-to-UART Product	2014-11-25 17:06:39 -08:00
8250_pnp.c	tty: delete non-required instances of include <linux/init.h>	2014-01-07 17:05:21 -08:00
8250.h	serial: 8250: sparse warning of incorrect type	2014-11-06 14:58:28 -08:00
Kconfig	serial: ralink: adds Mediatek MT7620 serial	2014-11-06 14:57:18 -08:00
Makefile	tty: serial: Add 8250-core based omap driver	2014-11-05 19:05:13 -08:00
serial_cs.c	tty: delete non-required instances of include <linux/init.h>	2014-01-07 17:05:21 -08:00