title: CPU soft lock up - NMI watchdog: BUG: soft lockup
body: <p>My Linux kernel version is, <code>4.1.52</code>. The processor architecture is <code>arm</code>.
  Though the <code>Comm</code> field in the report shows <code>testd</code> which is my application, I dont think that could cause this issue. I believe the issue is in the kernel space itself. Refering to the back trace at the last part of the screen capture, I suspect <code>testd</code> was crashing and that triggered a CPU soft lock up. Following is the crash report.</p>
  <pre><code>NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [testd:6556]
  [685228.664372] CPU: 1 PID: 6556 Comm: testd Tainted: P                4.1.52 #1
  [685228.664373] Hardware name: XXXXXXX (XX)
  [685228.664375] task: ffffffc00c4a4ac0 ti: ffffffc00988c000 task.ti: ffffffc00988c000
  [685228.664387] PC is at _raw_spin_unlock+0x20/0x40
  [685228.664394] LR is at ubifs_budget_space+0x4f4/0x5d0
  [685228.664396] pc : [&lt;ffffffc0005d5730&gt;] lr : [&lt;ffffffc00026d3d4&gt;] pstate: 00000145
  [685228.664397] sp : ffffffc00988f640
  [685228.664400] x29: ffffffc00988f640 x28: ffffffc01dd87000 
  [685228.664403] x27: ffffffc00988f718 x26: 00000000ffffffe4 
  [685228.664405] x25: 0000000000001ff8 x24: ffffffc0009f1f90 
  [685228.664408] x23: ffffffc000603000 x22: ffffffc01dd87920 
  [685228.664410] x21: 0000000000000000 x20: 0000000000000000 
  [685228.664413] x19: 00000000000000a0 x18: 0000000000000000 
  [685228.664415] x17: 0000000000000000 x16: ffffffc0000f8ce8 
  [685228.664418] x15: 0000000000000000 x14: 00000000f5ac9920 
  [685228.664420] x13: 0000000000000002 x12: 0000000000000000 
  [685228.664422] x11: 0000000000000001 x10: 0000000000000000 
  [685228.664425] x9 : ffffffc00988f590 x8 : ffffffc00c4a5030 
  [685228.664427] x7 : ffffffc01eb26000 x6 : 000000007ffff000 
  [685228.664430] x5 : ffffffffffffffff x4 : 0000000000000001 
  [685228.664432] x3 : 0000000000000000 x2 : 0000000000000000 
  [685228.664434] x1 : ffffffc00988c000 x0 : 0000000000000001 
  [685228.664435] 
  [685228.664437] Kernel panic - not syncing: softlockup: hung tasks
  [685228.664440] CPU: 1 PID: 6556 Comm: testd Tainted: P             L  4.1.52 #1
  [685228.664441] Hardware name: XXXXXXX (XX)
  [685228.664443] Call trace:
  [685228.664450] [&lt;ffffffc0000871c0&gt;] dump_backtrace+0x0/0x150
  [685228.664454] [&lt;ffffffc000087324&gt;] show_stack+0x14/0x20
  [685228.664457] [&lt;ffffffc0005d096c&gt;] dump_stack+0x90/0xb0
  [685228.664462] [&lt;ffffffc0005ce0a4&gt;] panic+0xd8/0x220
  [685228.664468] [&lt;ffffffc0001088d8&gt;] watchdog+0x0/0x48
  [685228.664473] [&lt;ffffffc0000e04c0&gt;] hrtimer_run_queues+0xa8/0x1e0
  [685228.664476] [&lt;ffffffc0000dfb84&gt;] update_process_times+0x2c/0x70
  [685228.664482] [&lt;ffffffc0000ed330&gt;] tick_nohz_handler+0x80/0x108
  [685228.664488] [&lt;ffffffc0003f2638&gt;] arch_timer_handler_phys+0x30/0x40
  [685228.664493] [&lt;ffffffc0000d5998&gt;] handle_percpu_devid_irq+0x78/0xa0
  [685228.664496] [&lt;ffffffc0000d14b4&gt;] generic_handle_irq+0x34/0x50
  [685228.664498] [&lt;ffffffc0000d17c4&gt;] __handle_domain_irq+0x5c/0xb8
  [685228.664501] [&lt;ffffffc000080c18&gt;] gic_handle_irq+0x38/0x90
  [685228.664504] Exception stack(0xffffffc00988f4f0 to 0xffffffc00988f620)
  [685228.664507] f4e0:                                     000000a0 00000000 00000000 00000080
  [685228.664511] f500: 0988f640 ffffffc0 005d5730 ffffffc0 00000001 00000000 0988c000 ffffffc0
  [685228.664515] f520: 00000000 00000000 00000000 00000000 00000001 00000000 ffffffff ffffffff
  [685228.664519] f540: 7ffff000 00000000 1eb26000 ffffffc0 0c4a5030 ffffffc0 0988f590 ffffffc0
  [685228.664522] f560: 00000000 00000000 00000001 00000000 00000000 00000000 00000002 00000000
  [685228.664526] f580: f5ac9920 00000000 00000000 00000000 000f8ce8 ffffffc0 00000000 00000000
  [685228.664529] f5a0: 00000000 00000000 000000a0 00000000 00000000 00000000 00000000 00000000
  [685228.664533] f5c0: 1dd87920 ffffffc0 00603000 ffffffc0 009f1f90 ffffffc0 00001ff8 00000000
  [685228.664537] f5e0: ffffffe4 00000000 0988f718 ffffffc0 1dd87000 ffffffc0 0988f640 ffffffc0
  [685228.664541] f600: 0026d3d4 ffffffc0 0988f640 ffffffc0 005d5730 ffffffc0 00000145 00000000
  [685228.664544] [&lt;ffffffc000083f00&gt;] el1_irq+0x80/0xf8
  [685228.664548] [&lt;ffffffc00026d3d4&gt;] ubifs_budget_space+0x4f4/0x5d0
  [685228.664553] [&lt;ffffffc0002573a8&gt;] ubifs_write_iter+0x88/0x180
  [685228.664558] [&lt;ffffffc000159e70&gt;] __vfs_write+0xa8/0x108
  [685228.664560] [&lt;ffffffc000159f14&gt;] __kernel_write+0x44/0x110
  [685228.664564] [&lt;ffffffc000402154&gt;] crashdump_write+0x44/0x88
  [685228.664567] [&lt;ffffffc000402b60&gt;] crashdump_sync_buf+0x160/0x218
  [685228.664570] [&lt;ffffffc000402e4c&gt;] crash_zdump_write+0x14/0x28
  [685228.664576] [&lt;ffffffc0001aa3d8&gt;] dump_emit+0x130/0x160
  [685228.664580] [&lt;ffffffc0001a7074&gt;] elf_core_dump+0xfa4/0x10e8
  [685228.664583] [&lt;ffffffc0001aaba8&gt;] do_coredump+0x620/0x1108
  [685228.664589] [&lt;ffffffc0000a0560&gt;] get_signal+0x2a8/0x530
  [685228.664592] [&lt;ffffffc00008697c&gt;] do_signal+0x194/0x4f8
  [685228.664595] [&lt;ffffffc000086ed4&gt;] do_notify_resume+0x64/0x70
  </code></pre>