GDB中打印pthread_internal_t的方法

每个进程所有pthread_internal_t结构是用g_thread_list链起来的。因此可以通过这个静态变量来查找想要的pthread_internal_t，如：

(gdb) p  g_thread_list
$87 = (pthread_internal_t *) 0x7f6a51a450
(gdb) p *g_thread_list
$88 = {
  next = 0x7f69bc6450, 
  prev = 0x0, 
  tid = 31561, 
  cached_pid_ = 1448, 
  attr = {
    flags = 1, 
    stack_base = 0x7f6a41e000, 
    stack_size = 1033296, 
    guard_size = 4096, 
    sched_policy = 0, 
    sched_priority = 0, 
    __reserved = " REf1770000002020253k1770000"
  }, 
  join_state = THREAD_DETACHED, 
  cleanup_stack = 0x0, 
  start_routine = 0x7f97147cd0 <thread_data_t::trampoline(thread_data_t const*)>, 
  start_routine_arg = 0x7f66455260, 
  return_value = 0x0, 
  alternate_signal_stack = 0x0, 
  startup_handshake_lock = {
    state = Lock::Unlocked, 
    process_shared = false
  }, 
  mmap_size = 1036288, 
  thread_local_dtors = 0x0, 
  tls = {0x7f6a51a4e8, 0x7f6a51a450, 0x0, 0x0, 0x0, 0x2212c0df7ebda00b, 0x0, 0x0, 0x0}, 
  key_data = {{
      seq = 0, 
      data = 0x0
    } <repeats 141 times>}, 
  dlerror_buffer = '00' <repeats 511 times>
}

(gdb) p *(pthread_internal_t *)0x7f69bc6450
$91 = {
  next = 0x7f6b695450, 
  prev = 0x7f6a51a450, 
  tid = 30974, 
  cached_pid_ = 1448, 
  attr = {
    flags = 1, 
    stack_base = 0x7f69aca000, 
    stack_size = 1033296, 
    guard_size = 4096, 
    sched_policy = 0, 
    sched_priority = 0, 
    __reserved = "v240275~33730022"310362O2221770000"
  }, 
  join_state = THREAD_DETACHED, 
  cleanup_stack = 0x0, 
  start_routine = 0x7f943ca7b4 <__timer_thread_start(void*)>, 
  start_routine_arg = 0x7f75b694f0, 
  return_value = 0x0, 
  alternate_signal_stack = 0x7f6e6c1000, 
  startup_handshake_lock = {
    state = Lock::LockedWithoutWaiter, 
    process_shared = false
  }, 
  mmap_size = 1036288, 
  thread_local_dtors = 0x0, 
  tls = {0x7f69bc64e8, 0x7f69bc6450, 0x0, 0x0, 0x0, 0x2212c0df7ebda00b, 0x0, 0x0, 0x0}, 
  key_data = {{
      seq = 0, 
      data = 0x0
    } <repeats 141 times>}, 
  dlerror_buffer = '00' <repeats 511 times>
}

pthread_internal_t中有很多有用的数据可供我们分析和调试问题。

如果需要通过tid或者栈指针获取对应的pthread_internal_t，可以用以下脚本实现：

define print_thread_by_tid
    set $tid = $arg0
    set $pThread = g_thread_list

    while $pThread != 0 
         if $pThread->tid == $tid
             p $pThread
             p *$pThread
             loop_break
         end 
         set $pThread = $pThread->next
    end
end

define print_thread_by_sp
    set $cursp = $arg0
    set $pThread = g_thread_list
    
    while $pThread != 0
       if $pThread->attr.stack_base <= $cursp && $pThread->attr.stack_base + $pThread->attr.stack_size >= $cursp
           p $pThread
           p *$pThread
           loop_break
       end 
       set $pThread = $pThread->next
    end
end

如果要找当前线程的pthread_internal_t，则可以利用当前的sp，如：

define print_current_thread
    print_thread_by_sp $sp
end

运行结果：

(gdb) print_current_thread 
$92 = (pthread_internal_t *) 0x7f6b466450
$93 = {
  next = 0x7f6987a450, 
  prev = 0x7f6ad59450, 
  tid = 2047, 
  cached_pid_ = 1448, 
  attr = {
    flags = 1, 
    stack_base = 0x7f6b36a000, 
    stack_size = 1033296, 
    guard_size = 4096, 
    sched_policy = 0, 
    sched_priority = 0, 
    __reserved = "20025324u177000000@3732123111770000"
  }, 
  join_state = THREAD_DETACHED, 
  cleanup_stack = 0x0, 
  start_routine = 0x7f97147cd0 <thread_data_t::trampoline(thread_data_t const*)>, 
  start_routine_arg = 0x7f75d415a0, 
  return_value = 0x0, 
  alternate_signal_stack = 0x7f721be000, 
  startup_handshake_lock = {
    state = Lock::LockedWithoutWaiter, 
    process_shared = false
  }, 
  mmap_size = 1036288, 
  thread_local_dtors = 0x0, 
  tls = {0x7f6b4664e8, 0x7f6b466450, 0x0, 0x7f954ad7f0 <android::gHooks+9224>, 0x0, 0x2212c0df7ebda00b, 0x0, 0x7f76239200, 0x0}, 
  key_data = {{
      seq = 1, 
      data = 0x7f75d40080
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 1, 
      data = 0x7f86abe180
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 1, 
      data = 0x7f76018010
    }, {
      seq = 1, 
      data = 0x7f75d42fa0
    }, {
      seq = 1, 
      data = 0x7f75d9dc00
    }, {
      seq = 0, 
      data = 0x0
    }, {
      seq = 1, 
      data = 0x7f67be29a0
    }, {
      seq = 1, 
      data = 0x7f67917c50
    }, {
      seq = 0, 
      data = 0x0
    } <repeats 119 times>}, 
  dlerror_buffer = '00' <repeats 511 times>
}