| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 011/112] x86/mm/ptdump: Fix soft lockup in page table walker | Date | Tue, 27 Oct 2020 14:48:41 +0100 |
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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
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> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20170210095405.31802-1-aryabinin@virtuozzo.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> [bwh: Backported to 4.4: adjust context] Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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++; }
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