x86/mm/ptdump: Fix soft lockup in page table walker
authorAndrey Ryabinin <aryabinin@virtuozzo.com>
Fri, 10 Feb 2017 09:54:05 +0000 (12:54 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 14 Feb 2017 23:25:41 +0000 (15:25 -0800)
commitc3cc4259f8322fef4f59e719b05b07bc6833d8f9
treed8ac2e8141aff4aca3b0dd4ec98632545b4284a4
parent34f840fc0d8918fc015ee8bd8a2e1a457c7094e2
x86/mm/ptdump: Fix soft lockup in page table walker

commit 146fbb766934dc003fcbf755b519acef683576bf upstream.

CONFIG_KASAN=y needs a lot of virtual memory mapped for its shadow.
In that case ptdump_walk_pgd_level_core() takes a lot of time to
walk across all page tables and doing this without
a rescheduling causes soft lockups:

 NMI watchdog: BUG: soft lockup - CPU#3 stuck for 23s! [swapper/0:1]
 ...
 Call Trace:
  ptdump_walk_pgd_level_core+0x40c/0x550
  ptdump_walk_pgd_level_checkwx+0x17/0x20
  mark_rodata_ro+0x13b/0x150
  kernel_init+0x2f/0x120
  ret_from_fork+0x2c/0x40

I guess that this issue might arise even without KASAN on huge machines
with several terabytes of RAM.

Stick cond_resched() in pgd loop to fix this.

Reported-by: Tobias Regnery <tobias.regnery@gmail.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: kasan-dev@googlegroups.com
Cc: Alexander Potapenko <glider@google.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Link: http://lkml.kernel.org/r/20170210095405.31802-1-aryabinin@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/x86/mm/dump_pagetables.c