INFO: task hung in lru_add_drain_all_cpuslocked

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b859aa7d ANDROID: squashfs: resolve merge conflict with 4...
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=10eec7e1400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0bdd1b757a6ba0b
dashboard link: https://syzkaller.appspot.com/bug?extid=e4dd66f6577b22277656
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e4dd66...@syzkaller.appspotmail.com

INFO: task syz-executor3:23776 blocked for more than 140 seconds.
Not tainted 4.14.68+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3 D25784 23776 2049 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3548
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x521/0x1480 kernel/locking/mutex.c:893
lru_add_drain_all_cpuslocked+0x7f/0x450 mm/swap.c:704
lru_add_drain_all+0xf/0x20 mm/swap.c:730
do_mlock+0x8c/0x5c0 mm/mlock.c:673
SYSC_mlock mm/mlock.c:713 [inline]
SyS_mlock+0x1d/0x30 mm/mlock.c:711
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x457099
RSP: 002b:00007f2f0a64fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000095
RAX: ffffffffffffffda RBX: 00007f2f0a6506d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 0000000000002000 RDI: 0000000020ffc000
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d3120 R14: 00000000004c814b R15: 0000000000000000
INFO: task syz-executor3:23779 blocked for more than 140 seconds.
Not tainted 4.14.68+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3 D27848 23779 2049 0x00000004
Call Trace:
schedule+0x7f/0x1b0 kernel/sched/core.c:3490
schedule_timeout+0x710/0xe60 kernel/time/timer.c:1718
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common+0x3bc/0x4e0 kernel/sched/completion.c:123
flush_work+0x3b8/0x6e0 kernel/workqueue.c:2885
lru_add_drain_all_cpuslocked+0x2ef/0x450 mm/swap.c:722
lru_add_drain_all+0xf/0x20 mm/swap.c:730
do_mlock+0x8c/0x5c0 mm/mlock.c:673
SYSC_mlock mm/mlock.c:713 [inline]
SyS_mlock+0x1d/0x30 mm/mlock.c:711
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x457099
RSP: 002b:00007f2f0a62ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000095
RAX: ffffffffffffffda RBX: 00007f2f0a62f6d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 0000000000002000 RDI: 0000000020ffc000
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d3120 R14: 00000000004c814b R15: 0000000000000001

Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [<ffffffff9d4019d7>]
debug_show_all_locks+0x74/0x20f kernel/locking/lockdep.c:4541
2 locks held by getty/1973:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff9df1c980>]
tty_ldisc_ref_wait+0x20/0x80 drivers/tty/tty_ldisc.c:275
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff9df17eff>]
n_tty_read+0x1ff/0x15e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor3/23776:
#0: (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff9d65f84a>]
get_online_cpus include/linux/cpu.h:138 [inline]
#0: (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff9d65f84a>]
lru_add_drain_all+0xa/0x20 mm/swap.c:729
#1: (lock#4){+.+.}, at: [<ffffffff9d65f46f>]
lru_add_drain_all_cpuslocked+0x7f/0x450 mm/swap.c:704
2 locks held by syz-executor3/23779:
#0: (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff9d65f84a>]
get_online_cpus include/linux/cpu.h:138 [inline]
#0: (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff9d65f84a>]
lru_add_drain_all+0xa/0x20 mm/swap.c:729
#1: (lock#4){+.+.}, at: [<ffffffff9d65f46f>]
lru_add_drain_all_cpuslocked+0x7f/0x450 mm/swap.c:704

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 23 Comm: khungtaskd Not tainted 4.14.68+ #4
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x11b lib/dump_stack.c:53
nmi_cpu_backtrace.cold.0+0x47/0x85 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x121/0x146 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:196 [inline]
watchdog+0x574/0xa70 kernel/hung_task.c:252
kthread+0x348/0x420 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 23732 Comm: syz-executor4 Not tainted 4.14.68+ #4
task: ffff88017ab80000 task.stack: ffff88017ab88000
RIP: 0010:___bpf_prog_run+0xc5/0x5c70 kernel/bpf/core.c:885
RSP: 0018:ffff88017ab8f9b0 EFLAGS: 00000246
RAX: 00000000000000af RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 1ffffffff3e12be3 RSI: ffffc90000529030 RDI: ffffffff9f095f18
RBP: ffff88017ab8fae0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff9f0959a0
R13: 1ffff1002f571f3d R14: ffffed002f571f62 R15: ffffc90000529030
FS: 00007f6914f7e700(0000) GS:ffff8801dba00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000000 CR3: 000000019f4b4006 CR4: 00000000001606b0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
Code: 03 83 e2 07 0f b6 04 18 38 d0 7f 08 84 c0 0f 85 a0 3e 00 00 41 0f b6
07 48 8d 3c c5 a0 59 09 9f 48 89 fa 48 c1 ea 03 80 3c 1a 00 <0f> 85 71 3e
00 00 49 8b 04 c4 e9 2c 42 86 01 e8 d7 c6 f6 ff 48


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.