Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

On Tue, 2019-10-15 at 20:51 +0530, Anshuman Khandual wrote:

quoted

On 10/15/2019 08:11 PM, Qian Cai wrote:

quoted

The x86 will crash with linux-next during boot due to this series (v5) with the
config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
it.

https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config

[   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
[   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
[   33.871140][    T1]  ? rest_init+0x307/0x307
[   33.871140][    T1]  kernel_init+0x11/0x139
[   33.871140][    T1]  ? rest_init+0x307/0x307
[   33.871140][    T1]  ret_from_fork+0x27/0x50
[   33.871140][    T1] Modules linked in:
[   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
[   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490

Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
with the config above, it does. Just wondering if it is possible that these
pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?

Yes, this patch works fine.

diff --git a/init/main.c b/init/main.c
index 676d8020dd29..591be8f9e8e0 100644
--- a/init/main.c
+++ b/init/main.c

@@ -1177,7 +1177,6 @@ static noinline void __init kernel_init_freeable(void)

        workqueue_init();
 
        init_mm_internals();
-       debug_vm_pgtable();
 
        do_pre_smp_initcalls();
        lockup_detector_init();

@@ -1186,6 +1185,8 @@ static noinline void __init kernel_init_freeable(void)

        sched_init_smp();
 
        page_alloc_init_late();
+       debug_vm_pgtable();
+
        /* Initialize page ext after all struct pages are initialized. */
        page_ext_init();