BUG: soft lockup in rcu_is_watching

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17c9f302b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=1da4e6e1fb85d130626e
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1da4e6...@syzkaller.appspotmail.com

watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:23668]
Modules linked in:
irq event stamp: 2583811
hardirqs last enabled at (2583810): [<ffffffff881950e9>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
hardirqs last enabled at (2583810): [<ffffffff881950e9>] _raw_spin_unlock_irqrestore+0x79/0xe0 kernel/locking/spinlock.c:184
hardirqs last disabled at (2583811): [<ffffffff81003d00>] trace_hardirqs_off_thunk+0x1a/0x1c
softirqs last enabled at (248): [<ffffffff87008a38>] read_pnet include/net/net_namespace.h:307 [inline]
softirqs last enabled at (248): [<ffffffff87008a38>] sock_net include/net/sock.h:2436 [inline]
softirqs last enabled at (248): [<ffffffff87008a38>] unix_create1+0x458/0x530 net/unix/af_unix.c:833
softirqs last disabled at (293): [<ffffffff813927d5>] invoke_softirq kernel/softirq.c:372 [inline]
softirqs last disabled at (293): [<ffffffff813927d5>] irq_exit+0x215/0x260 kernel/softirq.c:412
CPU: 0 PID: 23668 Comm: syz-executor.1 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:348 [inline]
RIP: 0010:rcu_is_watching+0x3a/0xc0 kernel/rcu/tree.c:1025
Code: 25 02 48 c7 c3 c0 2a 02 00 48 ba 00 00 00 00 00 fc ff df 89 c0 48 8d 3c c5 00 af cf 89 48 89 f9 48 c1 e9 03 80 3c 11 00 75 6d <48> 03 1c c5 00 af cf 89 be 04 00 00 00 48 8d 6b 10 48 89 ef e8 5d
RSP: 0018:ffff8880ba007cf0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: 0000000000022ac0 RCX: 1ffffffff139f5e0
RDX: dffffc0000000000 RSI: ffffffff83771e31 RDI: ffffffff89cfaf00
RBP: ffff8880576365c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: ffff8880ba007d58
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88805114b1a8
FS: 00007f934130b700(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff410adcd7 CR3: 000000004c0d5000 CR4: 00000000003406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
rcu_read_lock_sched_held+0xc6/0x1d0 kernel/rcu/update.c:113
trace_timer_expire_exit include/trace/events/timer.h:121 [inline]
call_timer_fn+0x617/0x700 kernel/time/timer.c:1339
expire_timers+0x243/0x4e0 kernel/time/timer.c:1375
__run_timers kernel/time/timer.c:1696 [inline]
run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1709
__do_softirq+0x265/0x980 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x215/0x260 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1098
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline]
RIP: 0010:generic_exec_single+0x317/0x490 kernel/smp.c:154
Code: 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 5a 01 00 00 48 83 3d 61 04 99 08 00 0f 84 db 00 00 00 e8 3e 07 0a 00 48 89 df 57 9d <0f> 1f 44 00 00 45 31 e4 e9 39 fe ff ff e8 27 07 0a 00 0f 0b e9 3a
RSP: 0018:ffff88802548fb08 EFLAGS: 00000216 ORIG_RAX: ffffffffffffff13
RAX: 0000000000040000 RBX: 0000000000000216 RCX: ffffc90007e3d000
RDX: 00000000000009a6 RSI: ffffffff81587e32 RDI: 0000000000000216
RBP: 0000000000000200 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88802548fb80
R13: ffff88802548fc40 R14: ffffffff81767200 R15: ffff8880576365fc
smp_call_function_single+0x1cf/0x420 kernel/smp.c:299
task_function_call+0xe0/0x170 kernel/events/core.c:115
perf_install_in_context+0x238/0x3c0 kernel/events/core.c:2623
__do_sys_perf_event_open kernel/events/core.c:10924 [inline]
__se_sys_perf_event_open+0xe5d/0x2720 kernel/events/core.c:10549
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f9343d95a39
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:00007f934130b188 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f9343ea8f60 RCX: 00007f9343d95a39
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000000020000180
RBP: 00007f9343defe8f R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffefd6a746f R14: 00007f934130b300 R15: 0000000000022000
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 48 c7 c3 c0 2a 02 00 mov $0x22ac0,%rbx
7: 48 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%rdx
e: fc ff df
11: 89 c0 mov %eax,%eax
13: 48 8d 3c c5 00 af cf lea -0x76305100(,%rax,8),%rdi
1a: 89
1b: 48 89 f9 mov %rdi,%rcx
1e: 48 c1 e9 03 shr $0x3,%rcx
22: 80 3c 11 00 cmpb $0x0,(%rcx,%rdx,1)
26: 75 6d jne 0x95
* 28: 48 03 1c c5 00 af cf add -0x76305100(,%rax,8),%rbx <-- trapping instruction
2f: 89
30: be 04 00 00 00 mov $0x4,%esi
35: 48 8d 6b 10 lea 0x10(%rbx),%rbp
39: 48 89 ef mov %rbp,%rdi
3c: e8 .byte 0xe8
3d: 5d pop %rbp


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[syzbot]

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