Below is a snippet from "perf" report taken for gnome-panel high cpu issue (cpu spins on below mutex for gnome-panel process)
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g_type_check_instance_is_a  /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0                                                                       
  1.69 │       xor    %eax,%eax                                                                                                                       ▒
       │       test   %r8,%r8                                                                                                                         ▒
       │     ↓ je     9b                                                                                                                              ▒
  1.69 │ 3c:   testb  $0x4,0x16(%r8)                                                                                                                  ▒
 13.48 │     ↓ je     b0                                                                                                                              ▒
  2.25 │       test   %rsi,%rsi                                                                                                                       ▒
  0.56 │     ↓ je     b0                                                                                                                              ◆
  0.56 │       movzbl 0x14(%rsi),%eax                                                                                                                 ▒
  6.18 │       movzbl 0x14(%r8),%edx                                                                                                                  ▒
  1.12 │       cmp    %dl,%al                                                                                                                         ▒
  1.12 │     ↓ ja     65                                                                                                                              ▒
  2.25 │       sub    %eax,%edx                                                                                                                       ▒
       │       mov    0x48(%rsi),%rdi                                                                                                                 ▒
  2.25 │       movslq %edx,%rdx                                                                                                                       ▒
       │       cmp    %rdi,0x48(%r8,%rdx,8)                                                                                                           ▒
 18.54 │     ↓ je     a2                                                                                                                              ▒
       │ 65:   cltq                                                                                                                                   ▒
       │       cmpq   $0x8,0x48(%rsi,%rax,8)                                                                                                          ▒
       │     ↓ je     b8                                                                                                                              ▒
       │ 6f:   xor    %eax,%eax                                                                                                                       ▒
       │     ← retq                                                                                                                                   ▒
       │       nop                                                                                                                                    ▒
  1.12 │ 78:   and    $0xfffffffffffffffc,%r8                                                                                                         ▒
  1.12 │       cmp    $0x3fc,%rsi                                                                                                                     ▒
       │     ↑ ja     31                                                                                                                              ▒
       │ 85:   lea    g_param_spec_types+0x78,%rax                                                                                                    ▒
  2.25 │       shr    $0x2,%rsi                                                                                                                       ▒
       │       mov    (%rax,%rsi,8),%rsi                                                                                                              ▒
  3.93 │       xor    %eax,%eax                                                                                                                       ▒
       │       test   %r8,%r8                                                                                                                         ▒
  0.56 │     ↑ jne    3c                                                                                                                              ▒
       │ 9b:   repz   retq                                                                                                                            ▒
       │ 9d:   test   %r9,%r9                                                                                                                         ▒
       │     ↑ je     6f                                                                                                                              ▒
  2.25 │ a2:   mov    $0x1,%eax 

Also,
pthread_mutex_lock  /lib/x86_64-linux-gnu/libpthread-2.19.so                                                                                           
       │       lea    default_barrierattr+0x38,%rdi
       │       mov    $0x74,%edx
       │     → callq  __assert_fail@plt
       │11f:   mov    0x4(%rdi),%eax
  0.50 │       cmp    $0xffffffff,%eax
  0.25 │     ↓ je     1d5
       │       add    $0x1,%eax
  0.25 │       mov    %eax,0x4(%rdi)
       │       xor    %eax,%eax
       │     ↑ jmpq   8b
  0.50 │138:   cmp    $0x3,%eax
  0.50 │     ↓ jne    1f9
  0.50 │       cmpl   $0x0,__is_smp
  0.99 │     ↑ je     58
       │       mov    %edx,%eax
  0.25 │       mov    $0x1,%edx
       │       lock   cmpxchg %edx,(%rdi)
 25.50 │       test   %eax,%eax
       │     ↓ je     1ab
       │       movswl 0x14(%rdi),%eax
       │       mov    $0x1,%esi
       │       lea    0xa(%rax,%rax,1),%ecx
       │       mov    $0x64,%eax
       │       cmp    $0x64,%ecx
       │       cmovg  %eax,%ecx
       │       xor    %dl,%dl
       │       xor    %edi,%edi
  0.74 │179:   add    $0x1,%edx
       │       lea    -0x1(%rdx),%eax
       │       cmp    %eax,%ecx
       │     ↓ jle    1df