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Date: Tue, 16 Apr 2024 10:54:17 -0700
From: Jane Chu <jane.chu@...cle.com>
To: Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc: naoya.horiguchi@....com, osalvador@...e.de, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/memory-failure: fix deadlock when
hugetlb_optimize_vmemmap is enabled
On 4/11/2024 7:57 PM, Miaohe Lin wrote:
> When I did hard offline test with hugetlb pages, below deadlock occurs:
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.8.0-11409-gf6cef5f8c37f #1 Not tainted
> ------------------------------------------------------
> bash/46904 is trying to acquire lock:
> ffffffffabe68910 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_slow_dec+0x16/0x60
>
> but task is already holding lock:
> ffffffffabf92ea8 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable+0x16/0x40
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (pcp_batch_high_lock){+.+.}-{3:3}:
> __mutex_lock+0x6c/0x770
> page_alloc_cpu_online+0x3c/0x70
> cpuhp_invoke_callback+0x397/0x5f0
> __cpuhp_invoke_callback_range+0x71/0xe0
> _cpu_up+0xeb/0x210
> cpu_up+0x91/0xe0
> cpuhp_bringup_mask+0x49/0xb0
> bringup_nonboot_cpus+0xb7/0xe0
> smp_init+0x25/0xa0
> kernel_init_freeable+0x15f/0x3e0
> kernel_init+0x15/0x1b0
> ret_from_fork+0x2f/0x50
> ret_from_fork_asm+0x1a/0x30
>
> -> #0 (cpu_hotplug_lock){++++}-{0:0}:
> __lock_acquire+0x1298/0x1cd0
> lock_acquire+0xc0/0x2b0
> cpus_read_lock+0x2a/0xc0
> static_key_slow_dec+0x16/0x60
> __hugetlb_vmemmap_restore_folio+0x1b9/0x200
> dissolve_free_huge_page+0x211/0x260
> __page_handle_poison+0x45/0xc0
> memory_failure+0x65e/0xc70
> hard_offline_page_store+0x55/0xa0
> kernfs_fop_write_iter+0x12c/0x1d0
> vfs_write+0x387/0x550
> ksys_write+0x64/0xe0
> do_syscall_64+0xca/0x1e0
> entry_SYSCALL_64_after_hwframe+0x6d/0x75
>
> other info that might help us debug this:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(pcp_batch_high_lock);
> lock(cpu_hotplug_lock);
> lock(pcp_batch_high_lock);
> rlock(cpu_hotplug_lock);
>
> *** DEADLOCK ***
>
> 5 locks held by bash/46904:
> #0: ffff98f6c3bb23f0 (sb_writers#5){.+.+}-{0:0}, at: ksys_write+0x64/0xe0
> #1: ffff98f6c328e488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0xf8/0x1d0
> #2: ffff98ef83b31890 (kn->active#113){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x100/0x1d0
> #3: ffffffffabf9db48 (mf_mutex){+.+.}-{3:3}, at: memory_failure+0x44/0xc70
> #4: ffffffffabf92ea8 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable+0x16/0x40
>
> stack backtrace:
> CPU: 10 PID: 46904 Comm: bash Kdump: loaded Not tainted 6.8.0-11409-gf6cef5f8c37f #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
> Call Trace:
> <TASK>
> dump_stack_lvl+0x68/0xa0
> check_noncircular+0x129/0x140
> __lock_acquire+0x1298/0x1cd0
> lock_acquire+0xc0/0x2b0
> cpus_read_lock+0x2a/0xc0
> static_key_slow_dec+0x16/0x60
> __hugetlb_vmemmap_restore_folio+0x1b9/0x200
> dissolve_free_huge_page+0x211/0x260
> __page_handle_poison+0x45/0xc0
> memory_failure+0x65e/0xc70
> hard_offline_page_store+0x55/0xa0
> kernfs_fop_write_iter+0x12c/0x1d0
> vfs_write+0x387/0x550
> ksys_write+0x64/0xe0
> do_syscall_64+0xca/0x1e0
> entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7fc862314887
> Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
> RSP: 002b:00007fff19311268 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007fc862314887
> RDX: 000000000000000c RSI: 000056405645fe10 RDI: 0000000000000001
> RBP: 000056405645fe10 R08: 00007fc8623d1460 R09: 000000007fffffff
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000c
> R13: 00007fc86241b780 R14: 00007fc862417600 R15: 00007fc862416a00
>
> In short, below scene breaks the lock dependency chain:
>
> memory_failure
> __page_handle_poison
> zone_pcp_disable -- lock(pcp_batch_high_lock)
> dissolve_free_huge_page
> __hugetlb_vmemmap_restore_folio
> static_key_slow_dec
> cpus_read_lock -- rlock(cpu_hotplug_lock)
>
> Fix this by calling drain_all_pages() instead.
>
> Fixes: a6b40850c442 ("mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> Acked-by: Oscar Salvador <osalvador@...e.de>
> Cc: <stable@...r.kernel.org>
> ---
> v2:
> collect Acked-by tag and extend comment per Oscar. Thanks.
> ---
> mm/memory-failure.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index edd6e114462f..c6750509d74c 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -153,11 +153,21 @@ static int __page_handle_poison(struct page *page)
> {
> int ret;
>
> - zone_pcp_disable(page_zone(page));
> + /*
> + * zone_pcp_disable() can't be used here. It will hold pcp_batch_high_lock and
> + * dissolve_free_huge_page() might hold cpu_hotplug_lock via static_key_slow_dec()
> + * when hugetlb vmemmap optimization is enabled. This will break current lock
> + * dependency chain and leads to deadlock.
> + * Disabling pcp before dissolving the page was a deterministic approach because
> + * we made sure that those pages cannot end up in any PCP list. Draining PCP lists
> + * expels those pages to the buddy system, but nothing guarantees that those pages
> + * do not get back to a PCP queue if we need to refill those.
> + */
> ret = dissolve_free_huge_page(page);
> - if (!ret)
> + if (!ret) {
> + drain_all_pages(page_zone(page));
> ret = take_page_off_buddy(page);
> - zone_pcp_enable(page_zone(page));
> + }
>
> return ret;
> }
Looks good.
Reviewed-by: Jane Chu <jane.chu@...cle.com>
-jane
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