Binder子系统之调试分析(三)

一. binder调试信息

1.1 binder_thread

调用方法:print_binder_thread

thread 8980: l 12 //tid=8980，looper=12

关于looper状态值:

BINDER_LOOPER_STATE_REGISTERED  = 0x01, // 创建注册线程BC_REGISTER_LOOPER
BINDER_LOOPER_STATE_ENTERED     = 0x02, // 创建主线程BC_ENTER_LOOPER
BINDER_LOOPER_STATE_EXITED      = 0x04, // 已退出
BINDER_LOOPER_STATE_INVALID     = 0x08, // 非法
BINDER_LOOPER_STATE_WAITING     = 0x10, // 等待中
BINDER_LOOPER_STATE_NEED_RETURN = 0x20, // 需要返回

所以0x12 = BINDER_LOOPER_STATE_ENTERED | BINDER_LOOPER_STATE_WAITING，代表的是等待就绪状态且由为binder主线程. 简单说,looper值, 十位为1代表处于binder_thread_read()状态, 个位为1代表已注册的binder线程,个位为2代表binder主线程.

1.2 binder_node

关于binder_node的输出信息:print_binder_node()

例如:

node 3079465: u0000005593cc3540 c0000005593f37030 hs 1 hw 1 ls 0 lw 0 is 1 iw 1 proc 8963

含义:

debug_id = 3079465
ptr = u0000005593cc3540
cookies = c0000005593f37030
has_strong_ref(hs) = 1
has_weak_ref(hw) = 1
local_strong_refs(ls) = 0
local_weak_refs(lw) = 0
internal_strong_refs(is) = 1
count: (node->refs总引用次数) = 1
proc: (node->refs->proc->pid) = 8963

1.3 binder_ref

调用方法: print_binder_ref()

//含义：ref `debug_id`:`desc` `node` `node->debug_id` `strong` `weak` `death`
ref 340122: desc 1 node 340121 s 1 w 1 d ffffffc04f90a340

输出binder_ref结构体成员变量:

node是指当 ref->node->proc为空则代表node已死亡,采用deadnode,否则node.
death: 应用注册死亡通知时，此域不为空.

1.4 binder_buffer

调用方法: print_binder_buffer()

//含义：buffer `debug_id`:`data` `data_size`:`offsets_size` `transaction`
buffer 3473176: ffffff8007700218 size 0:0 delivered

输出的便是binder_buffer结构体的成员变量,其中transaction不为空,则为active,否则为delivered.

1.5 binder_transaction

print_binder_transaction

static void print_binder_transaction(struct seq_file *m, const char *prefix,struct binder_transaction *t)
{seq_printf(m,"%s %d: %p from %d:%d to %d:%d code %x flags %x pri %ld r%d",prefix, t->debug_id, t,t->from ? t->from->proc->pid : 0,t->from ? t->from->pid : 0,t->to_proc ? t->to_proc->pid : 0,t->to_thread ? t->to_thread->pid : 0,t->code, t->flags, t->priority, t->need_reply);if (t->buffer == NULL) {seq_puts(m, " buffer free\n");return;}if (t->buffer->target_node)seq_printf(m, " node %d",t->buffer->target_node->debug_id);seq_printf(m, " size %zd:%zd data %p\n",t->buffer->data_size, t->buffer->offsets_size,t->buffer->data);
}

接下来,分别说说系统中几个常见进程:surfaceflinger, mediaserver, servicemanager,system_server

二. mediaserver

    USER      PID   PPID  VSIZE  RSS   WCHAN              PC  NAMEmedia     8814  1     128376 16068 binder_thr 00f6da2db0 S /system/bin/mediaservermedia     9304  8814  128376 16068 binder_thr 00f6da2db0 S Binder_1media     9305  8814  128376 16068 binder_thr 00f6da2db0 S Binder_2media     22609 8814  128376 16068 binder_thr 00f6da2db0 S Binder_3

2.1 stats

proc 8814threads: 8requested threads: 0+2/15ready threads 4free async space 520192nodes: 13refs: 14 s 14 w 14buffers: 0pending transactions: 0

进程mediaserver:

处于ready状态的binder线程个数为4:
BC_ENTER_LOOPER创建2个binder线程
BC_REGISTER_LOOPER创建2个binder线程

2.2 proc/8814

proc 8814thread 8814: l 12thread 9294: l 00thread 9296: l 00thread 9297: l 00thread 9299: l 00thread 9304: l 12thread 9305: l 11thread 22609: l 11

三. servicemanager

单线程的进程:

system    435   1     3872   1040  binder_thr 7fb462bcd4 S /system/bin/servicemanagerproc 435threads: 1requested threads: 0+0/0ready threads 1free async space 65536nodes: 1refs: 130 s 130 w 0buffers: 0pending transactions: 0proc 435thread 435: l 12node 1: u0000000000000000 c0000000000000000 hs 1 hw 1 ls 1 lw 1 is 72 iw 72 proc ...

该binder_thread是由BC_ENTER_LOOPER所创建的binder主线程, 只有一个binder_node对象, 被72个进程所使用.servicemanager作为服务管家,被系统大量进程所使用.

四. system_server

system    8963  8794  2337380 139776 SyS_epoll_ 7f950f2be4 S system_server
system    8980  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_1
system    8981  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_2
system    9407  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_3
system    9411  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_4
system    9472  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_5
system    9513  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_6
system    9590  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_7
system    9591  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_8
system    9592  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_9
system    9594  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_A
system    9596  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_B
system    9860  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_C
system    9862  8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_D
system    10074 8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_E
system    10081 8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_F
system    10082 8963  2337092 138556 binder_thr 7f950f2cd4 S Binder_10

4.1 stats

proc 8963threads: 50requested threads: 0+15/15ready threads 16free async space 520192nodes: 596refs: 951 s 950 w 950buffers: 3pending transactions: 0

进程system_server:

- 处于ready状态的binder线程个数为16:
- BC_ENTER_LOOPER创建1个binder线程
- BC_REGISTER_LOOPER创建15个binder线程

4.2 proc/8963

proc 8963thread 8963: l 00thread 8976: l 00thread 8980: l 12thread 8981: l 11...buffer 3263909: ffffff8007700150 size 8:0 deliveredbuffer 3468983: ffffff80077001a8 size 24:8 deliveredbuffer 3473176: ffffff8007700218 size 0:0 delivered

8976作为binder主线程,已使用的binder buffer个数为3.

五. surfaceflinger

system    492   436   192320 21360 binder_thr 7f99cffcd4 S Binder_2
system    3068  436   192320 21360 binder_thr 7f99cffcd4 S Binder_3
system    4063  436   192320 21360 binder_thr 7f99cffcd4 S Binder_4
system    8317  436   192320 21360 binder_thr 7f99cffcd4 S Binder_5

5.1 stats

proc 436threads: 8requested threads: 0+4/4ready threads 5free async space 520192nodes: 50refs: 6 s 5 w 6buffers: 0pending transactions: 0...

进程surfaceflinger:

处于ready状态的binder线程个数为5:
BC_ENTER_LOOPER创建1个binder主线程
BC_REGISTER_LOOPER创建4个binder线程
max_threads = 4
binder_thread个数为8
已分配的buffer个数为0

5.2 proc/436

  proc 436thread 436: l 00thread 490: l 12thread 492: l 11thread 499: l 00thread 500: l 00thread 3068: l 11thread 4063: l 11thread 8317: l 11node 3079465: u0000005593cc3540 c0000005593f37030 hs 1 hw 1 ls 0 lw 0 is 1 iw 1 proc 8963node 3076788: u0000005593f270d0 c0000005594049818 hs 1 hw 1 ls 0 lw 0 is 2 iw 2 proc 9687 8963...ref 18: desc 0 node 1 s 1 w 1 d           (null)ref 340122: desc 1 node 340121 s 1 w 1 d ffffffc04f90a340...

已知该进程有8个binder_thread,其中

4个线程处于0x11 = BINDER_LOOPER_STATE_REGISTERED | BINDER_LOOPER_STATE_WAITING,代表的是等待就绪状态
1个线程处于0x12 = BINDER_LOOPER_STATE_ENTERED | BINDER_LOOPER_STATE_WAITING,代表的是等待就绪状态

六. 小结

mediaserver和servicemanager的主线程都是binder线程; surfaceflinger和system_server的主线程并非binder线程
binder线程分为binder主线程和binder普通线程, binder主线程一般是binder_1或者进程的主线程.
cat /d/binder/stats和cat /d/binder/proc/<pid>是分析系统binder状态的重要信息.

本文举例的这几个重要进程情况：

进程	max	BC_REGISTER_LOOPER	BC_REGISTER_LOOPER
surfaceflinger	4	4	1
mediaserver	15	2	2
servicemanager	0	1	0
system_server	15	15	1

BC_REGISTER_LOOPER + BC_ENTER_LOOPER = max + 1，则代表该进程中的binder线程已达上限。可见, mediaserver具有继续创建新线程的能力,而其他几个进程都以达到可创建的binder线程上限.

原文地址：　http://gityuan.com/2016/09/03/binder-debug-3/