Re: [PATCH 1/3] mm, meminit: Recalculate pcpu batch and high limits after init completes

Michal Hocko
2019-10-21T14:12:32Z

On Mon 21-10-19 10:01:24, Qian Cai wrote:
>
>
> > On Oct 21, 2019, at 5:48 AM, Mel Gorman <mgorman@techsingularity.net> wrote:
i[...]
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index c0b2e0306720..f972076d0f6b 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1947,6 +1947,14 @@ void __init page_alloc_init_late(void)
> > /* Block until all are initialised */
> > wait_for_completion(&pgdat_init_all_done_comp);
> >
> > + /*
> > + * The number of managed pages has changed due to the initialisation
> > + * so the pcpu batch and high limits needs to be updated or the limits
> > + * will be artificially small.
> > + */
> > + for_each_populated_zone(zone)
> > + zone_pcp_update(zone);
> > +
> > /*
> > * We initialized the rest of the deferred pages. Permanently disable
> > * on-demand struct page initialization.
> > --
> > 2.16.4
> >
> >
>
> Warnings from linux-next,
>
> [ 14.265911][ T659] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:935
> [ 14.265992][ T659] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 659, name: pgdatinit8
> [ 14.266044][ T659] 1 lock held by pgdatinit8/659:
> [ 14.266075][ T659] #0: c000201ffca87b40 (&(&pgdat->node_size_lock)->rlock){....}, at: deferred_init_memmap+0xc4/0x26c

This is really surprising to say the least. I do not see any spinlock
held here. Besides that we do sleep in wait_for_completion already.
Is it possible that the patch has been misplaced? zone_pcp_update is
called from page_alloc_init_late which is a different context than
deferred_init_memmap which runs in a separate kthread.

> [ 14.266160][ T659] irq event stamp: 26
> [ 14.266194][ T659] hardirqs last enabled at (25): [<c000000000950584>] _raw_spin_unlock_irq+0x44/0x80
> [ 14.266246][ T659] hardirqs last disabled at (26): [<c0000000009502ec>] _raw_spin_lock_irqsave+0x3c/0xa0
> [ 14.266299][ T659] softirqs last enabled at (0): [<c0000000000ff8d0>] copy_process+0x720/0x19b0
> [ 14.266339][ T659] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [ 14.266400][ T659] CPU: 64 PID: 659 Comm: pgdatinit8 Not tainted 5.4.0-rc4-next-20191021 #1
> [ 14.266462][ T659] Call Trace:
> [ 14.266494][ T659] [c00000003d8efae0] [c000000000921cf4] dump_stack+0xe8/0x164 (unreliable)
> [ 14.266538][ T659] [c00000003d8efb30] [c000000000157c54] ___might_sleep+0x334/0x370
> [ 14.266577][ T659] [c00000003d8efbb0] [c00000000094a784] __mutex_lock+0x84/0xb20
> [ 14.266627][ T659] [c00000003d8efcc0] [c000000000954038] zone_pcp_update+0x34/0x64
> [ 14.266677][ T659] [c00000003d8efcf0] [c000000000b9e6bc] deferred_init_memmap+0x1b8/0x26c
> [ 14.266740][ T659] [c00000003d8efdb0] [c000000000149528] kthread+0x1a8/0x1b0
> [ 14.266792][ T659] [c00000003d8efe20] [c00000000000b748] ret_from_kernel_thread+0x5c/0x74
> [ 14.268288][ T659] node 8 initialised, 1879186 pages in 12200ms
> [ 14.268527][ T659] pgdatinit8 (659) used greatest stack depth: 27984 bytes left
> [ 15.589983][ T658] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:935
> [ 15.590041][ T658] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 658, name: pgdatinit0
> [ 15.590078][ T658] 1 lock held by pgdatinit0/658:
> [ 15.590108][ T658] #0: c000001fff5c7b40 (&(&pgdat->node_size_lock)->rlock){....}, at: deferred_init_memmap+0xc4/0x26c
> [ 15.590192][ T658] irq event stamp: 18
> [ 15.590224][ T658] hardirqs last enabled at (17): [<c000000000950654>] _raw_spin_unlock_irqrestore+0x94/0xd0
> [ 15.590283][ T658] hardirqs last disabled at (18): [<c0000000009502ec>] _raw_spin_lock_irqsave+0x3c/0xa0
> [ 15.590332][ T658] softirqs last enabled at (0): [<c0000000000ff8d0>] copy_process+0x720/0x19b0
> [ 15.590379][ T658] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [ 15.590414][ T658] CPU: 8 PID: 658 Comm: pgdatinit0 Tainted: G W 5.4.0-rc4-next-20191021 #1
> [ 15.590460][ T658] Call Trace:
> [ 15.590491][ T658] [c00000003d8cfae0] [c000000000921cf4] dump_stack+0xe8/0x164 (unreliable)
> [ 15.590541][ T658] [c00000003d8cfb30] [c000000000157c54] ___might_sleep+0x334/0x370
> [ 15.590588][ T658] [c00000003d8cfbb0] [c00000000094a784] __mutex_lock+0x84/0xb20
> [ 15.590643][ T658] [c00000003d8cfcc0] [c000000000954038] zone_pcp_update+0x34/0x64
> [ 15.590689][ T658] [c00000003d8cfcf0] [c000000000b9e6bc] deferred_init_memmap+0x1b8/0x26c
> [ 15.590739][ T658] [c00000003d8cfdb0] [c000000000149528] kthread+0x1a8/0x1b0
> [ 15.590790][ T658] [c00000003d8cfe20] [c00000000000b748] ret_from_kernel_thread+0x5c/0x74

--
Michal Hocko
SUSE Labs