This is a note to let you know that I've just added the patch titled
x86/mm/ptdump: Fix soft lockup in page table walker
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mm-ptdump-fix-soft-lockup-in-page-table-walker.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Oct 22 03:56:50 PM CEST 2020
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Date: Fri, 10 Feb 2017 12:54:05 +0300
Subject: x86/mm/ptdump: Fix soft lockup in page table walker
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: kasan-dev@xxxxxxxxxxxxxxxx
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170210095405.31802-1-aryabinin@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/dump_pagetables.c | 2 ++
1 file changed, 2 insertions(+)
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -15,6 +15,7 @@
#include <linux/debugfs.h>
#include <linux/mm.h>
#include <linux/module.h>
+#include <linux/sched.h>
#include <linux/seq_file.h>
#include <asm/pgtable.h>
@@ -407,6 +408,7 @@ static void ptdump_walk_pgd_level_core(s
} else
note_page(m, &st, __pgprot(0), 1);
+ cond_resched();
start++;
}
Patches currently in stable-queue which might be from aryabinin@xxxxxxxxxxxxx are
queue-4.4/x86-mm-ptdump-fix-soft-lockup-in-page-table-walker.patch
queue-4.4/mm-kasan-add-api-to-check-memory-regions.patch
queue-4.4/compiler.h-add-read_word_at_a_time-function.patch
queue-4.4/compiler.h-kasan-avoid-duplicating-__read_once_size_nocheck.patch
queue-4.4/mm-kasan-print-name-of-mem-caller-in-report.patch
queue-4.4/lib-strscpy-shut-up-kasan-false-positives-in-strscpy.patch
