INFO: rcu detected stall in seq

INFO: rcu detected stall in seq_read (2)
Status: upstream: reported C repro on 2020/07/22 18:02
Reported-by: syzbot+c28b5fee66fd3b7f766e@syzkaller.appspotmail.com
First crash: 91d, last: 1d07h

Cause bisection: introduced by (bisect log):

commit 53e233ea2fa9fa7e2405e95070981f327d90e519
Author: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Date: Thu Oct 4 05:43:52 2018 +0000

devlink: Add Documentation/networking/devlink-params-bnxt.txt

Crash: general protection fault in batadv_iv_ogm_queue_add (log)
Repro: C syz .config

similar bugs (1):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
upstream	INFO: rcu detected stall in seq_read			1	397d	397d	0/17	auto-closed as invalid on 2019/12/18 18:14

Sample crash report:

hrtimer: interrupt took 6305559 ns
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 GPs behind) idle=91e/1/0x4000000000000000 softirq=10105/10107 fqs=1 
	(t=18319 jiffies g=8905 q=457)
NMI backtrace for cpu 1
CPU: 1 PID: 4008 Comm: systemd-journal Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x194/0x1cf kernel/rcu/tree_stall.h:320
 print_cpu_stall kernel/rcu/tree_stall.h:553 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:627 [inline]
 rcu_pending kernel/rcu/tree.c:3489 [inline]
 rcu_sched_clock_irq.cold+0x5b3/0xccc kernel/rcu/tree.c:2504
 update_process_times+0x25/0x60 kernel/time/timer.c:1737
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x108/0x290 kernel/time/tick-sched.c:1320
 __run_hrtimer kernel/time/hrtimer.c:1520 [inline]
 __hrtimer_run_queues+0x1d5/0xfc0 kernel/time/hrtimer.c:1584
 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1646
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0x142/0x5e0 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0xe0/0x120 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
RIP: 0010:format_decode+0x0/0xad0 lib/vsprintf.c:2329
Code: c7 c7 10 05 af 8a be 10 00 00 00 e8 5a c3 46 00 48 c7 c7 20 78 0d 8a e9 6e f2 e2 fd 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 <41> 57 41 56 41 55 41 54 55 48 89 f5 53 48 bb 00 00 00 00 00 fc ff
RSP: 0018:ffffc90001077a10 EFLAGS: 00000293
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffff83b0a497
RDX: ffff888093224040 RSI: ffffc90001077a80 RDI: ffffffff884e6293
RBP: ffffffff884e6293 R08: 0000000000000001 R09: ffff8880952a63d1
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880952a63d2
R13: ffffffff884e6293 R14: 0000000000000025 R15: ffffc90001077b30
 vsnprintf+0x155/0x14f0 lib/vsprintf.c:2572
 seq_vprintf fs/seq_file.c:379 [inline]
 seq_printf+0x195/0x240 fs/seq_file.c:394
 proc_pid_status+0x1c6d/0x24b0 fs/proc/array.c:424
 proc_single_show+0x116/0x1e0 fs/proc/base.c:766
 seq_read+0x432/0x1070 fs/seq_file.c:208
 vfs_read+0x1df/0x520 fs/read_write.c:479
 ksys_read+0x12d/0x250 fs/read_write.c:607
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f0fc43d9910
Code: Bad RIP value.
RSP: 002b:00007ffdcb193978 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000055b1476b96f0 RCX: 00007f0fc43d9910
RDX: 0000000000000800 RSI: 000055b1476b8b00 RDI: 0000000000000013
RBP: 00007f0fc4694440 R08: 00007f0fc4697fc8 R09: 0000000000000410
R10: 000055b1476b96f0 R11: 0000000000000246 R12: 0000000000000800
R13: 0000000000000d68 R14: 000055b1476b8b00 R15: 00007f0fc4693900

Fix bisection attempts:
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-kasan-gce	2020/10/19 13:42	upstream	7cf726a5	d88894e6	.config	log	report	syz	C
ci-upstream-kasan-gce	2020/09/19 13:16	upstream	eb5f95f1	d88894e6	.config	log		syz	C
ci-upstream-kasan-gce	2020/08/20 12:47	upstream	7eac66d0	d88894e6	.config	log	report	syz	C

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Maintainers
ci-upstream-kasan-gce	2020/07/21 12:22	upstream	4fa640dc	d88894e6	.config	log	report	syz	C		fweisbec@gmail.com, linux-kernel@vger.kernel.org, mingo@kernel.org, tglx@linutronix.de