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Date:   Mon, 23 Nov 2020 19:54:52 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     syzbot <syzbot+e5a33e700b1dd0da20a2@syzkaller.appspotmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        syzkaller-bugs@googlegroups.com,
        Alex Shi <alex.shi@linux.alibaba.com>
Subject: Re: INFO: task can't die in shrink_inactive_list (2)
Message-Id: <20201123195452.8ecd01b1fc2ce287dfd6a0d5@linux-foundation.org>
In-Reply-To: <0000000000000340a105b49441d3@google.com>
References: <0000000000000340a105b49441d3@google.com>
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On Fri, 20 Nov 2020 17:55:22 -0800 syzbot <syzbot+e5a33e700b1dd0da20a2@syzkaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    03430750 Add linux-next specific files for 20201116
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13f80e5e500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a1c4c3f27041fdb8
> dashboard link: https://syzkaller.appspot.com/bug?extid=e5a33e700b1dd0da20a2
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12f7bc5a500000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10934cf2500000

Alex, your series "per memcg lru lock" changed the vmscan code rather a
lot.  Could you please take a look at that reproducer?

> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e5a33e700b1dd0da20a2@syzkaller.appspotmail.com
> 
> INFO: task syz-executor880:8534 can't die for more than 143 seconds.
> task:syz-executor880 state:R  running task     stack:25304 pid: 8534 ppid:  8504 flags:0x00004006
> Call Trace:
>  context_switch kernel/sched/core.c:4269 [inline]
>  __schedule+0x890/0x2030 kernel/sched/core.c:5019
>  preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:5179
>  preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:40
>  __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
>  _raw_spin_unlock_irq+0x3c/0x40 kernel/locking/spinlock.c:199
>  spin_unlock_irq include/linux/spinlock.h:404 [inline]
>  shrink_inactive_list+0x4b1/0xce0 mm/vmscan.c:1974
>  shrink_list mm/vmscan.c:2167 [inline]
>  shrink_lruvec+0x61b/0x11b0 mm/vmscan.c:2462
>  shrink_node_memcgs mm/vmscan.c:2650 [inline]
>  shrink_node+0x839/0x1d60 mm/vmscan.c:2767
>  shrink_zones mm/vmscan.c:2970 [inline]
>  do_try_to_free_pages+0x38b/0x1440 mm/vmscan.c:3025
>  try_to_free_pages+0x29f/0x720 mm/vmscan.c:3264
>  __perform_reclaim mm/page_alloc.c:4360 [inline]
>  __alloc_pages_direct_reclaim mm/page_alloc.c:4381 [inline]
>  __alloc_pages_slowpath.constprop.0+0x917/0x2510 mm/page_alloc.c:4785
>  __alloc_pages_nodemask+0x5f0/0x730 mm/page_alloc.c:4995
>  alloc_pages_current+0x191/0x2a0 mm/mempolicy.c:2271
>  alloc_pages include/linux/gfp.h:547 [inline]
>  __page_cache_alloc mm/filemap.c:977 [inline]
>  __page_cache_alloc+0x2ce/0x360 mm/filemap.c:962
>  page_cache_ra_unbounded+0x3a1/0x920 mm/readahead.c:216
>  do_page_cache_ra+0xf9/0x140 mm/readahead.c:267
>  do_sync_mmap_readahead mm/filemap.c:2721 [inline]
>  filemap_fault+0x19d0/0x2940 mm/filemap.c:2809
>  __do_fault+0x10d/0x4d0 mm/memory.c:3623
>  do_shared_fault mm/memory.c:4071 [inline]
>  do_fault mm/memory.c:4149 [inline]
>  handle_pte_fault mm/memory.c:4385 [inline]
>  __handle_mm_fault mm/memory.c:4520 [inline]
>  handle_mm_fault+0x3033/0x55d0 mm/memory.c:4618
>  do_user_addr_fault+0x55b/0xba0 arch/x86/mm/fault.c:1377
>  handle_page_fault arch/x86/mm/fault.c:1434 [inline]
>  exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1490
>  asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:580
> RIP: 0033:0x400e71
> Code: Unable to access opcode bytes at RIP 0x400e47.
> RSP: 002b:00007f8a5353fdc0 EFLAGS: 00010246
> RAX: 6c756e2f7665642f RBX: 00000000006dbc38 RCX: 0000000000402824
> RDX: 928195da81441750 RSI: 0000000000000000 RDI: 00000000006dbc30
> RBP: 00000000006dbc30 R08: 0000000000000000 R09: 00007f8a53540700
> R10: 00007f8a535409d0 R11: 0000000000000202 R12: 00000000006dbc3c
> R13: 00007ffe80747a5f R14: 00007f8a535409c0 R15: 0000000000000001
> 
> Showing all locks held in the system:
> 1 lock held by khungtaskd/1659:
>  #0: ffffffff8b339ce0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6252
> 1 lock held by kswapd0/2195:
> 1 lock held by kswapd1/2196:
> 1 lock held by in:imklog/8191:
>  #0: ffff8880125b1270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:932
> 1 lock held by cron/8189:
> 2 locks held by syz-executor880/8502:
> 2 locks held by syz-executor880/8505:
> 2 locks held by syz-executor880/8507:
> 2 locks held by syz-executor880/11706:
> 2 locks held by syz-executor880/11709:
> 3 locks held by syz-executor880/12008:
> 2 locks held by syz-executor880/12015:
> 
> =============================================
> 
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches