linux/arch/arc
Vineet Gupta ab6c03676c ARC: show_regs: lockdep: avoid page allocator...
and use smaller/on-stack buffer instead

The motivation for this change was lockdep splat like below.

| potentially unexpected fatal signal 11.
| BUG: sleeping function called from invalid context at ../mm/page_alloc.c:4317
| in_atomic(): 1, irqs_disabled(): 0, pid: 57, name: segv
| no locks held by segv/57.
| Preemption disabled at:
| [<8182f17e>] get_signal+0x4a6/0x7c4
| CPU: 0 PID: 57 Comm: segv Not tainted 4.17.0+ #23
|
| Stack Trace:
|  arc_unwind_core.constprop.1+0xd0/0xf4
|  __might_sleep+0x1f6/0x234
|  __get_free_pages+0x174/0xca0
|  show_regs+0x22/0x330
|  get_signal+0x4ac/0x7c4     # print_fatal_signals() -> preempt_disable()
|  do_signal+0x30/0x224
|  resume_user_mode_begin+0x90/0xd8

So signal handling core calls show_regs() with preemption disabled but
an ensuing GFP_KERNEL page allocator call is flagged by lockdep.

We could have switched to GFP_NOWAIT, but turns out that is not enough
anways and eliding page allocator call leads to less code and
instruction traces to sift thru when debugging pesky crashes.

FWIW, this patch doesn't cure the lockdep splat (which next patch does).

Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
2019-01-17 14:38:00 -08:00
..
boot ARC: [plat-hsdk] Enable DW APB GPIO support 2018-11-12 10:38:27 -08:00
configs ARC: change defconfig defaults to ARCv2 2018-11-30 10:54:01 -08:00
include ARC: perf: map generic branches to correct hardware condition 2019-01-17 14:38:00 -08:00
kernel ARC: show_regs: lockdep: avoid page allocator... 2019-01-17 14:38:00 -08:00
lib ARC: dw2 unwind: enable cfi pseudo ops in string lib 2016-09-30 14:48:22 -07:00
mm ARC: adjust memblock_reserve of kernel memory 2019-01-17 14:38:00 -08:00
oprofile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
plat-axs10x PCI: consolidate PCI config entry in drivers/pci 2018-11-23 11:45:34 +09:00
plat-eznps arc: [plat-eznps] fix printk warning in arc/plat-eznps/mtm.c 2018-07-30 11:48:49 -07:00
plat-hsdk PCI: consolidate PCI config entry in drivers/pci 2018-11-23 11:45:34 +09:00
plat-sim ARC: [plat-sim] Include this platform unconditionally 2017-08-04 13:49:47 +05:30
plat-tb10x arc: select GPIOLIB directly 2016-04-26 14:07:59 +02:00
Kbuild
Kconfig Kconfig file consolidation for v4.21 2018-12-29 13:40:29 -08:00
Kconfig.debug Kconfig: consolidate the "Kernel hacking" menu 2018-08-02 08:06:48 +09:00
Makefile ARC: change defconfig defaults to ARCv2 2018-11-30 10:54:01 -08:00