[syzbot] INFO: rcu detected stall in snd_seq_write (2)

From: syzbot
Date: Sun Oct 31 2021 - 13:20:31 EST


Hello,

syzbot found the following issue on:

HEAD commit: bdcc9f6a5682 Add linux-next specific files for 20211029
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17e542a6b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=4b504bcb4c507265
dashboard link: https://syzkaller.appspot.com/bug?extid=bb950e68b400ab4f65f8
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16e913bab00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bb950e68b400ab4f65f8@xxxxxxxxxxxxxxxxxxxxxxxxx

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-....: (1 GPs behind) idle=9f5/1/0x4000000000000000 softirq=16474/16475 fqs=4916
(t=10500 jiffies g=19249 q=192515)
NMI backtrace for cpu 1
CPU: 1 PID: 13283 Comm: syz-executor.4 Not tainted 5.15.0-rc7-next-20211029-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:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x1ae/0x220 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
rcu_dump_cpu_stacks+0x25e/0x3f0 kernel/rcu/tree_stall.h:343
print_cpu_stall kernel/rcu/tree_stall.h:604 [inline]
check_cpu_stall kernel/rcu/tree_stall.h:688 [inline]
rcu_pending kernel/rcu/tree.c:3922 [inline]
rcu_sched_clock_irq.cold+0x9d/0x746 kernel/rcu/tree.c:2620
update_process_times+0x16d/0x200 kernel/time/timer.c:1785
tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226
tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1428
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x1c0/0xe50 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x31c/0x790 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
__sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1103
sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1097
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:194
Code: 74 24 10 e8 fa 8e 42 f8 48 89 ef e8 42 05 43 f8 81 e3 00 02 00 00 75 25 9c 58 f6 c4 02 75 2d 48 85 db 74 01 fb bf 01 00 00 00 <e8> e3 cd 35 f8 65 8b 05 5c 26 e8 76 85 c0 74 0a 5b 5d c3 e8 40 c8
RSP: 0018:ffffc9000d36faf0 EFLAGS: 00000206
RAX: 0000000000000002 RBX: 0000000000000200 RCX: 1ffffffff1f54946
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffff888061a6c498 R08: 0000000000000001 R09: ffffffff8fa48af7
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000293 R14: ffff888061a6c498 R15: 0000000000000000
spin_unlock_irqrestore include/linux/spinlock.h:422 [inline]
snd_seq_prioq_cell_out+0x1dc/0x360 sound/core/seq/seq_prioq.c:238
snd_seq_check_queue+0x1a6/0x3f0 sound/core/seq/seq_queue.c:262
snd_seq_enqueue_event+0x1ed/0x3e0 sound/core/seq/seq_queue.c:334
snd_seq_client_enqueue_event.constprop.0+0x230/0x440 sound/core/seq/seq_clientmgr.c:976
snd_seq_write+0x388/0x690 sound/core/seq/seq_clientmgr.c:1096
vfs_write+0x28e/0xae0 fs/read_write.c:588
ksys_write+0x1ee/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f4c1777bae9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4c16ed0188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4c1788f020 RCX: 00007f4c1777bae9
RDX: 00000000fffffee4 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00007f4c177d5f25 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff0d94d1bf R14: 00007f4c16ed0300 R15: 0000000000022000
</TASK>
----------------
Code disassembly (best guess):
0: 74 24 je 0x26
2: 10 e8 adc %ch,%al
4: fa cli
5: 8e 42 f8 mov -0x8(%rdx),%es
8: 48 89 ef mov %rbp,%rdi
b: e8 42 05 43 f8 callq 0xf8430552
10: 81 e3 00 02 00 00 and $0x200,%ebx
16: 75 25 jne 0x3d
18: 9c pushfq
19: 58 pop %rax
1a: f6 c4 02 test $0x2,%ah
1d: 75 2d jne 0x4c
1f: 48 85 db test %rbx,%rbx
22: 74 01 je 0x25
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 e3 cd 35 f8 callq 0xf835ce12 <-- trapping instruction
2f: 65 8b 05 5c 26 e8 76 mov %gs:0x76e8265c(%rip),%eax # 0x76e82692
36: 85 c0 test %eax,%eax
38: 74 0a je 0x44
3a: 5b pop %rbx
3b: 5d pop %rbp
3c: c3 retq
3d: e8 .byte 0xe8
3e: 40 rex
3f: c8 .byte 0xc8


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