INFO: task hung in flush

INFO: task hung in flush_work
Status: upstream: reported C repro on 2018/05/07 15:47
Reported-by: syzbot+2e7b6af5956e05e5cff7@syzkaller.appspotmail.com
First crash: 1036d, last: 926d

Cause bisection: failed (bisect log)

duplicates (3):
Title	Repro	Count	Last	Reported	Patched	Status
INFO: task hung in utimes_common		23	873d	971d	0/21	closed as dup on 2018/07/18 11:44
INFO: task hung in vfs_removexattr		21	30d	972d	0/21	closed as dup on 2018/07/18 11:45
INFO: task hung in grab_super	C	205	675d	963d	0/21	closed as dup on 2018/07/18 11:42

similar bugs (3):
Kernel	Title	Repro	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	INFO: task hung in flush_work	C	inconclusive	5	280d	686d	0/1	upstream: reported C repro on 2019/04/21 07:04
android-49	INFO: task hung in flush_work	C		28	840d	694d	0/3	public: reported C repro on 2019/04/13 00:00
android-414	INFO: task hung in flush_work			11	700d	694d	0/1	auto-closed as invalid on 2019/10/04 01:39

Sample crash report:

INFO: task syz-executor810:4676 blocked for more than 140 seconds.
      Not tainted 4.18.0-rc4-next-20180711+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor810 D23936  4676   4481 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2853 [inline]
 __schedule+0x87c/0x1ed0 kernel/sched/core.c:3501
 schedule+0xfb/0x450 kernel/sched/core.c:3545
 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1777
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common kernel/sched/completion.c:115 [inline]
 wait_for_completion+0x430/0x8d0 kernel/sched/completion.c:136
 flush_work+0x531/0x900 kernel/workqueue.c:2918
 __cancel_work_timer+0x4bd/0x830 kernel/workqueue.c:2989
 cancel_work_sync+0x17/0x20 kernel/workqueue.c:3025
 p9_conn_destroy net/9p/trans_fd.c:860 [inline]
 p9_fd_close+0x36a/0x5b0 net/9p/trans_fd.c:886
 p9_client_create+0xa9a/0x1770 net/9p/client.c:1077
 v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
 v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
 legacy_get_tree+0x118/0x440 fs/fs_context.c:659
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1743
 do_new_mount fs/namespace.c:2567 [inline]
 do_mount+0x6c1/0x1fb0 fs/namespace.c:2889
 ksys_mount+0x12d/0x140 fs/namespace.c:3105
 __do_sys_mount fs/namespace.c:3119 [inline]
 __se_sys_mount fs/namespace.c:3116 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3116
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445e89
Code: Bad RIP value.
RSP: 002b:00007fd68625eda8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00000000006dbc3c RCX: 0000000000445e89
RDX: 0000000020000340 RSI: 00000000200000c0 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00000000200001c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00000000006dbc38
R13: 0030656c69662f2e R14: 64663d736e617274 R15: 0000000000000005
INFO: lockdep is turned off.
NMI backtrace for cpu 1
CPU: 1 PID: 901 Comm: khungtaskd Not tainted 4.18.0-rc4-next-20180711+ #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.3+0x48/0x88 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace include/linux/nmi.h:144 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:231 [inline]
 watchdog+0xb81/0x10f0 kernel/hung_task.c:292
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54

Crashes (306):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-linux-next-kasan-gce-root	2018/07/11 15:17	linux-next	98be4506	2e0e3130	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2018/08/24 14:30	upstream	33e17876	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/23 19:11	upstream	815f0ddb	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/23 11:03	upstream	899fbc33	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/23 00:36	upstream	ad1d6973	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/22 21:37	upstream	ad1d6973	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/22 08:22	upstream	0214f46b	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/22 07:23	upstream	0214f46b	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/21 11:48	upstream	778a3395	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/21 08:27	upstream	cc26ebbe	95b5c82b	.config	log	report
ci-upstream-kasan-gce-root	2018/08/20 08:53	upstream	2ad0d526	2dc4378f	.config	log	report
ci-upstream-kasan-gce-root	2018/08/19 22:07	upstream	08b5fa81	2dc4378f	.config	log	report
ci-upstream-kasan-gce-root	2018/08/19 07:11	upstream	a18d783f	de20bcbb	.config	log	report
ci-upstream-kasan-gce-root	2018/08/19 04:57	upstream	a18d783f	de20bcbb	.config	log	report
ci-upstream-kasan-gce-root	2018/08/18 18:23	upstream	1f7a4c73	db1858f6	.config	log	report
ci-upstream-kasan-gce-root	2018/08/18 15:48	upstream	1f7a4c73	db1858f6	.config	log	report
ci-upstream-kasan-gce-root	2018/08/17 17:16	upstream	5c60a738	738da825	.config	log	report
ci-upstream-kasan-gce-root	2018/08/17 10:54	upstream	5c60a738	9ccc1d45	.config	log	report
ci-upstream-kasan-gce-root	2018/08/17 08:23	upstream	5c60a738	9ccc1d45	.config	log	report
ci-upstream-kasan-gce-root	2018/08/16 23:20	upstream	f91e6544	9ccc1d45	.config	log	report
ci-upstream-kasan-gce-root	2018/08/16 02:35	upstream	dafa5f65	9ccc1d45	.config	log	report
ci-upstream-kasan-gce-root	2018/08/15 19:59	upstream	31130a16	9ccc1d45	.config	log	report
ci-upstream-kasan-gce-root	2018/08/14 07:08	upstream	77969161	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/14 02:51	upstream	77969161	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/14 00:13	upstream	77969161	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/13 13:36	upstream	94710cac	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/13 04:58	upstream	d6dd6431	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/12 23:27	upstream	d6dd6431	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/12 13:14	upstream	ec0c9671	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/12 09:00	upstream	ec0c9671	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/12 07:24	upstream	ec0c9671	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/12 04:56	upstream	ec0c9671	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/12 03:29	upstream	ec0c9671	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/11 15:04	upstream	f313b43b	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/11 13:54	upstream	f313b43b	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/11 12:14	upstream	f313b43b	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/11 00:55	upstream	f313b43b	7a88b141	.config	log	report
ci-upstream-kasan-gce-root	2018/08/10 16:37	upstream	112cbae2	1fb62d58	.config	log	report
ci-upstream-kasan-gce-root	2018/08/10 11:44	upstream	112cbae2	1fb62d58	.config	log	report
ci-upstream-kasan-gce	2018/07/16 00:31	upstream	9d3cce1e	92a49505	.config	log	report
ci-upstream-kasan-gce-386	2018/07/11 04:51	upstream	30c2c32d	2e0e3130	.config	log	report
ci-upstream-net-kasan-gce	2018/07/16 22:08	net-next	aea06eb2	40cb0c9a	.config	log	report
ci-upstream-net-kasan-gce	2018/05/06 20:42	net-next	8fb11a9a	6c18ddb0	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2018/08/17 23:50	linux-next	d7857ae4	738da825	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2018/08/17 12:04	linux-next	d7857ae4	9ccc1d45	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2018/08/15 20:02	linux-next	e5a7da82	9ccc1d45	.config	log	report
ci-upstream-kmsan-gce	2018/07/20 08:23	https://github.com/google/kmsan.git master	cf8cd3cd	49f35839	.config	log	report