linux_dsm_epyc7002/arch/arc/kernel
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
..
.gitignore ARC: Add some .gitignore entries 2013-08-26 09:40:24 +05:30
arc_hostlink.c ARC: Hostlink Pseudo-Driver for Metaware Debugger 2013-02-15 23:16:10 +05:30
arcksyms.c ARC: export __udivdi3 for modules 2016-08-19 14:09:33 -07:00
asm-offsets.c ARCv2: [vdk] dts files and defconfig for HS38 VDK 2015-06-25 06:00:21 +05:30
ctx_sw_asm.S ARC: dw2 unwind: enable cfi pseudo ops in string lib 2016-09-30 14:48:22 -07:00
ctx_sw.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
devtree.c ARC: [plat-hsdk] initial port for HSDK board 2017-09-01 11:26:28 -07:00
disasm.c ARC: rename kconfig option for unaligned emulation 2014-10-13 14:46:15 +05:30
entry-arcv2.S ARCv2: make unimplemented vectors as no-ops rather than halt core 2017-03-20 18:47:57 -07:00
entry-compact.S ARC: typos fix in kernel/entry-compact.S 2017-08-28 15:17:36 -07:00
entry.S ARC: Re-enable MMU upon Machine Check exception 2017-09-01 11:29:05 -07:00
fpu.c ARC: Process-creation/scheduling/idle-loop 2013-02-11 20:00:38 +05:30
head.S ARC: smp-boot: Decouple Non masters waiting API from jump to entry point 2017-01-24 11:12:28 -08:00
intc-arcv2.c ARCv2: SMP: Mask only private-per-core IRQ lines on boot at core intc 2017-08-28 16:11:15 -07:00
intc-compact.c ARCv2: SMP: Mask only private-per-core IRQ lines on boot at core intc 2017-08-28 16:11:15 -07:00
irq.c ARC: Enable machine_desc->init_per_cpu for !CONFIG_SMP 2018-06-20 16:12:06 -07:00
kgdb.c kgdb/treewide: constify struct kgdb_arch arch_kgdb_ops 2018-12-30 08:33:06 +00:00
kprobes.c bpf/error-inject/kprobes: Clear current_kprobe and enable preempt in kprobe 2018-06-21 12:33:19 +02:00
Makefile ARC: Remove empty kernel/pcibios.c 2017-08-02 14:53:35 -05:00
mcip.c ARC: mcip: update MCIP debug mask when the new cpu came online 2018-02-28 10:45:31 -08:00
module.c ARC: module: Fix !CONFIG_ARC_DW2_UNWIND builds 2017-01-18 11:17:44 -08:00
perf_event.c ARC: perf: avoid kernel killing where it is possible 2019-01-17 14:38:00 -08:00
process.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
ptrace.c ARCv2: ptrace: provide regset for accumulator/r30 regs 2017-05-03 11:21:31 -07:00
reset.c arc: export symbol for pm_power_off in reset.c 2013-11-06 10:41:44 +05:30
setup.c ARC: boot log: print Action point details 2019-01-17 14:38:00 -08:00
signal.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
smp.c ARC: setup cpu possible mask according to possible-cpus dts property 2018-02-28 10:45:32 -08:00
stacktrace.c arc: do not use __print_symbol() 2017-12-20 12:41:43 -08:00
sys.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
traps.c signal/arc: Push siginfo generation into unhandled_exception 2018-09-27 21:59:17 +02:00
troubleshoot.c ARC: show_regs: lockdep: avoid page allocator... 2019-01-17 14:38:00 -08:00
unaligned.c ARC: [arcompact] brown paper bag bug in unaligned access delay slot fixup 2017-02-07 10:02:01 -08:00
unwind.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
vmlinux.lds.S vmlinux.lds.h: Move LSM_TABLE into INIT_DATA 2018-10-10 20:40:21 -07:00