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Date:   Wed, 1 Apr 2020 17:45:49 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Shile Zhang <shile.zhang@linux.alibaba.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        Alexander Duyck <alexander.duyck@gmail.com>,
        Baoquan He <bhe@redhat.com>, Oscar Salvador <osalvador@suse.de>
Subject: Re: [PATCH v1 2/2] mm/page_alloc: fix watchdog soft lockups during
 set_zone_contiguous()
Message-ID: <20200401154549.GS22681@dhcp22.suse.cz>
References: <20200401104156.11564-1-david@redhat.com>
 <20200401104156.11564-3-david@redhat.com>
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On Wed 01-04-20 12:41:56, David Hildenbrand wrote:
> Without CONFIG_PREEMPT, it can happen that we get soft lockups detected,
> e.g., while booting up.
> 
> [  105.608900] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1]
> [  105.608933] Modules linked in:
> [  105.608933] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.6.0-next-20200331+ #4
> [  105.608933] Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
> [  105.608933] RIP: 0010:__pageblock_pfn_to_page+0x134/0x1c0
> [  105.608933] Code: 85 c0 74 71 4a 8b 04 d0 48 85 c0 74 68 48 01 c1 74 63 f6 01 04 74 5e 48 c1 e7 06 4c 8b 05 cc 991
> [  105.608933] RSP: 0000:ffffb6d94000fe60 EFLAGS: 00010286 ORIG_RAX: ffffffffffffff13
> [  105.608933] RAX: fffff81953250000 RBX: 000000000a4c9600 RCX: ffff8fe9ff7c1990
> [  105.608933] RDX: ffff8fe9ff7dab80 RSI: 000000000a4c95ff RDI: 0000000293250000
> [  105.608933] RBP: ffff8fe9ff7dab80 R08: fffff816c0000000 R09: 0000000000000008
> [  105.608933] R10: 0000000000000014 R11: 0000000000000014 R12: 0000000000000000
> [  105.608933] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> [  105.608933] FS:  0000000000000000(0000) GS:ffff8fe1ff400000(0000) knlGS:0000000000000000
> [  105.608933] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  105.608933] CR2: 000000000f613000 CR3: 00000088cf20a000 CR4: 00000000000006f0
> [  105.608933] Call Trace:
> [  105.608933]  set_zone_contiguous+0x56/0x70
> [  105.608933]  page_alloc_init_late+0x166/0x176
> [  105.608933]  kernel_init_freeable+0xfa/0x255
> [  105.608933]  ? rest_init+0xaa/0xaa
> [  105.608933]  kernel_init+0xa/0x106
> [  105.608933]  ret_from_fork+0x35/0x40
> 
> The issue becomes visible when having a lot of memory (e.g., 4TB)
> assigned to a single NUMA node - a system that can easily be created
> using QEMU. Inside VMs on a hypervisor with quite some memory
> overcommit, this is fairly easy to trigger.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
> Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Alexander Duyck <alexander.duyck@gmail.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  mm/page_alloc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 084cabffc90d..cc4f07d52939 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1607,6 +1607,7 @@ void set_zone_contiguous(struct zone *zone)
>  		if (!__pageblock_pfn_to_page(block_start_pfn,
>  					     block_end_pfn, zone))
>  			return;
> +		cond_resched();
>  	}
>  
>  	/* We confirm that there is no hole */
> -- 
> 2.25.1

-- 
Michal Hocko
SUSE Labs