INFO: task can't die in p9_client

INFO: task can't die in p9_client_rpc (2)
Status: auto-closed as invalid on 2021/02/14 08:07
Reported-by: syzbot+4ff9239a00671c7c656f@syzkaller.appspotmail.com
First crash: 232d, last: 221d

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	INFO: task can't die in p9_client_rpc				7	327d	357d	0/22	auto-closed as invalid on 2020/10/31 10:21
upstream	INFO: task can't die in p9_client_rpc (3)				4	26d	27d	0/22	upstream: reported on 2021/06/28 05:57

Sample crash report:

INFO: task syz-executor.2:25543 can't die for more than 143 seconds.
task:syz-executor.2  state:D stack:26712 pid:25543 ppid:  8521 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:4327 [inline]
 __schedule+0x8eb/0x21b0 kernel/sched/core.c:5078
 schedule+0xcf/0x270 kernel/sched/core.c:5157
 p9_client_rpc+0x400/0x1240 net/9p/client.c:759
 p9_client_flush+0x1f9/0x430 net/9p/client.c:667
 p9_client_rpc+0xfde/0x1240 net/9p/client.c:784
 p9_client_version net/9p/client.c:955 [inline]
 p9_client_create+0xae1/0x1110 net/9p/client.c:1055
 v9fs_session_init+0x1dd/0x1830 fs/9p/v9fs.c:406
 v9fs_mount+0x79/0x9c0 fs/9p/vfs_super.c:126
 legacy_get_tree+0x105/0x220 fs/fs_context.c:592
 vfs_get_tree+0x89/0x2f0 fs/super.c:1496
 do_new_mount fs/namespace.c:2896 [inline]
 path_mount+0x12ae/0x1e70 fs/namespace.c:3227
 do_mount fs/namespace.c:3240 [inline]
 __do_sys_mount fs/namespace.c:3448 [inline]
 __se_sys_mount fs/namespace.c:3425 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3425
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e159
RSP: 002b:00007f994339bc68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 000000000045e159
RDX: 0000000020000200 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000119c120 R08: 0000000020000600 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c0dc
R13: 00007ffcf2a0d07f R14: 00007f994339c9c0 R15: 000000000119c0dc

Showing all locks held in the system:
1 lock held by khungtaskd/1658:
 #0: ffffffff8b78f920 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x28c kernel/locking/lockdep.c:6254
1 lock held by systemd-journal/4906:
1 lock held by in:imklog/8198:
 #0: ffff88801d604370 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:923
2 locks held by agetty/8421:
 #0: ffff8880157b0098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:266
 #1: ffffc90000f882e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x21d/0x1ac0 drivers/tty/n_tty.c:2158
3 locks held by kworker/u4:2/8713:
 #0: ffff8880b9c34c58 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1318 [inline]
 #0: ffff8880b9c34c58 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x235/0x21b0 kernel/sched/core.c:4995
 #1: ffff8880b9c20088 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x305/0x440 kernel/sched/psi.c:833
 #2: ffff8880b9c24898 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x5a/0x1f0 kernel/time/timer.c:944
2 locks held by kworker/0:4/9045:
 #0: ffff8880b9c34c58 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1318 [inline]
 #0: ffff8880b9c34c58 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x235/0x21b0 kernel/sched/core.c:4995
 #1: ffff8880b9c20088 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x305/0x440 kernel/sched/psi.c:833

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

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-linux-next-kasan-gce-root	2020/12/16 08:06	linux-next	9317f948b0b1	f213e07e	.config	log	report			info
ci-upstream-linux-next-kasan-gce-root	2020/12/05 16:54	linux-next	0eedceafd3a6	50503117	.config	log	report			info