[load_elf_binary] WARNING: bad unlock balance detected!

[Fengguang Wu]

Hi,

Here is a warning in v4.14-rc8 -- it's not necessarily a new bug.

[   66.941105] 8021q: adding VLAN 0 to HW filter on device eth0
[   67.243706] 8021q: adding VLAN 0 to HW filter on device eth0
LKP: HOSTNAME vm-lkp-nex04-openwrt-ia32-4, MAC , kernel 4.14.0-rc8 158, serial console /dev/ttyS0
[   67.943691] 
[   67.944258] =====================================
[   67.945424] WARNING: bad unlock balance detected!
[   67.946566] 4.14.0-rc8 #158 Not tainted
[   67.947527] -------------------------------------
[   67.948461] grep/1361 is trying to release lock (rcu_preempt_state) at:
[   67.949772] [<c10e4348>] rcu_read_unlock_special+0x5f8/0x620
[   67.950843] but there are no more locks to release!
[   67.951839] 
[   67.951839] other info that might help us debug this:
[   67.953115] 2 locks held by grep/1361:
[   67.953881]  #0:  (&mm->mmap_sem){....}, at: [<c105194e>] __do_page_fault+0x2de/0xb40
[   67.955392]  #1:  (rcu_read_lock){....}, at: [<c11a5900>] find_get_entry+0x0/0x420
[   67.956841] 
[   67.956841] stack backtrace:
[   67.957765] CPU: 0 PID: 1361 Comm: grep Not tainted 4.14.0-rc8 #158
[   67.958944] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   67.960553] Call Trace:
[   67.962208]  dump_stack+0x16/0x1c
[   67.962949]  print_unlock_imbalance_bug+0xb9/0xd0
[   67.963871]  ? rcu_read_unlock_special+0x5f8/0x620
[   67.964908]  ? rcu_read_unlock_special+0x5f8/0x620
[   67.965847]  lock_release+0x1cc/0x490
[   67.966599]  ? rcu_read_unlock_special+0x5f8/0x620
[   67.967551]  ? _raw_spin_unlock_irqrestore+0x86/0xd0
[   67.968543]  rt_mutex_unlock+0x1e/0xb0
[   67.969312]  rcu_read_unlock_special+0x5f8/0x620
[   67.970280]  __rcu_read_unlock+0xa7/0xb0
[   67.971067]  find_get_entry+0x2ef/0x420
[   67.971856]  pagecache_get_page+0x1c/0x650
[   67.972684]  filemap_fault+0x105/0xd90
[   67.973468]  __do_fault+0x17/0x1d0
[   67.974176]  handle_mm_fault+0x1360/0x1d30
[   67.974994]  __do_page_fault+0x5a3/0xb40
[   67.975798]  ? kvm_read_and_reset_pf_reason+0x40/0x40
[   67.976777]  do_page_fault+0x30/0x250
[   67.977529]  ? kvm_read_and_reset_pf_reason+0x40/0x40
[   67.978500]  do_async_page_fault+0x2e/0xa0
[   67.979321]  common_exception+0x65/0x6a
[   67.980156] EIP: clear_user+0x128/0x170
[   67.980927] EFLAGS: 00010246 CPU: 0
[   67.981652] EAX: 00000000 EBX: 000003fe ECX: 000003fe EDX: 00000003
[   67.982821] ESI: b7fc0000 EDI: b7fbf005 EBP: ddda7e94 ESP: ddda7e80
[   67.984010]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
[   67.985058]  ? handle_mm_fault+0x700/0x1d30
[   67.985902]  ? kvm_read_and_reset_pf_reason+0x40/0x40
[   67.986881]  padzero+0x3c/0x60
[   67.987548]  load_elf_binary+0x1908/0x1bf0
[   67.988370]  ? _raw_read_unlock+0x55/0x90
[   67.989180]  search_binary_handler+0xd9/0x160
[   67.990102]  do_execveat_common+0x8f3/0xb10
[   67.990960]  SyS_execve+0x1f/0x30
[   67.991673]  do_int80_syscall_32+0x95/0x290
[   67.992508]  entry_INT80_32+0x2f/0x2f
[   67.993266] EIP: 0xb7f38b07
[   67.993866] EFLAGS: 00000296 CPU: 0
[   67.994627] EAX: ffffffda EBX: 08097394 ECX: 0809728c EDX: 080972a4
[   67.995831] ESI: 08097394 EDI: 080972a4 EBP: bfbeb778 ESP: bfbeb754
[   67.996998]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 007b
[   68.012659] grep (1361) used greatest stack depth: 6232 bytes left
[   69.303817] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX

Thanks,
Fengguang