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++; }
