skynet的启动 2014.11.05

bootstrap(..); 之前的代码没看懂

bootstrap()代码如下

static void
bootstrap( struct skynet_context * logger, const char * cmdline) {
     int sz = strlen(cmdline);
     char name[sz + 1 ];
     char args[sz + 1 ];
    sscanf(cmdline, " %s %s " , name, args);
     struct skynet_context * ctx = skynet_context_new(name, args);
     if (ctx == NULL) {
        skynet_error(NULL, " Bootstrap error : %s\n " , cmdline);
        skynet_context_dispatchall(logger);
        exit( 1 );
    }
}

一开始以为 skynet_context_new() 只是malloc()之类的调用而已
后来再看看 skynet_context_new() 的源码

struct skynet_context *
skynet_context_new( const char * name, const char * param) {
     struct skynet_module * mod = skynet_module_query(name);

     if (mod == NULL)
         return NULL;

     void * inst = skynet_module_instance_create(mod);
     if (inst == NULL)
         return NULL;
     struct skynet_context * ctx = skynet_malloc( sizeof ( * ctx));
    CHECKCALLING_INIT(ctx)

    ctx -> mod = mod;
    ctx -> instance = inst;
    ctx -> ref = 2 ;
    ctx -> cb = NULL;
    ctx -> cb_ud = NULL;
    ctx -> session_id = 0 ;
    ctx -> logfile = NULL;

    ctx -> init = false ;
    ctx -> endless = false ;
     // Should set to 0 first to avoid skynet_handle_retireall get an uninitialized handle
    ctx -> handle = 0 ;
    ctx -> handle = skynet_handle_register(ctx);
     struct message_queue * queue = ctx -> queue = skynet_mq_create(ctx -> handle);
     // init function maybe use ctx->handle, so it must init at last
    context_inc();

    CHECKCALLING_BEGIN(ctx)
     int r = skynet_module_instance_init(mod, inst, ctx, param);
    CHECKCALLING_END(ctx)
     if (r == 0 ) {
         struct skynet_context * ret = skynet_context_release(ctx);
         if (ret) {
            ctx -> init = true ;
        }
        skynet_globalmq_push(queue);
         if (ret) {
            skynet_error(ret, " LAUNCH %s %s " , name, param ? param : "" );
        }
         return ret;
    } else {
        skynet_error(ctx, " FAILED launch %s " , name);
        uint32_t handle = ctx -> handle;
        skynet_context_release(ctx);
        skynet_handle_retire(handle);
         struct drop_t d = { handle };
        skynet_mq_release(queue, drop_message, & d);
         return NULL;
    }
}

大概是进行了模块的初始化，并为这个模块创建消息队列, 并放到全局的队列里(注:模块初始化时会将 param 传进去)

之后开启线程,进行消息处理
_start(config->thread);

用GDB调试,看下堆栈

# 0   _init (l = 0x2b98570163a0 , ctx = 0x2b98570540f0 , args = 0x2b9857099070 " bootstrap " , sz = 9 ) at service - src / service_snlua.c: 71
# 1    0x00002b9857d02469 in _launch (context = 0x2b98570540f0 , ud = 0x2b98570163a0 , type = 0 , session = 0 , source = 16777218 , msg = 0x2b9857099070 , sz = 9 ) at service - src / service_snlua.c: 125
# 2    0x0000000000409546 in dispatch_message (ctx = 0x2b98570540f0 , msg = 0x420030e0 ) at skynet - src / skynet_server.c: 254
# 3    0x00000000004096c4 in skynet_context_message_dispatch (sm = 0x2b9857016440 , q = 0x2b98570530c0 , weight =- 1 ) at skynet - src / skynet_server.c: 308
# 4    0x000000000040a98f in _worker (p = 0x7fff54a5f8d0 ) at skynet - src / skynet_start.c: 128

为何会调用到 _launch? 回到前面

static void
bootstrap( struct skynet_context * logger, const char * cmdline) {
     int sz = strlen(cmdline);
     char name[sz + 1 ];
     char args[sz + 1 ];
    sscanf(cmdline, " %s %s " , name, args);
     struct skynet_context * ctx = skynet_context_new(name, args); // 这里传的参数分别为 snlua bootstrap
     if (ctx == NULL) {
        skynet_error(NULL, " Bootstrap error : %s\n " , cmdline);
        skynet_context_dispatchall(logger);
        exit( 1 );
    }
}

调用的流程是这样的

#0 _open_sym (mod=0x2b9e0a032438) at skynet-src/skynet_module.c:76
#1 0x0000000000408463 in skynet_module_query (name=0x7fffa16ae600 "snlua") at skynet-src/skynet_module.c:107
#2 0x0000000000409099 in skynet_context_new (name=0x7fffa16ae600 "snlua", param=0x7fffa16ae5e0 "bootstrap") at skynet-src/skynet_server.c:117
#3 0x000000000040adda in bootstrap (logger=0x2b9e0a054080, cmdline=0x2b9e0a0aa298 "snlua bootstrap") at skynet-src/skynet_start.c:204
#4 0x000000000040aedb in skynet_start (config=0x7fffa16ae6d0) at skynet-src/skynet_start.c:232
#5 0x000000000040751e in main (argc=2, argv=0x7fffa16ae7f8) at skynet-src/skynet_main.c:139

skynet_context_new 会先去 cservice目录下查找 snlua.so , 然后分别找
snlua_create ---> skynet_module->create
snlua_init ---> skynet_module->init
snlua_release ---> skynet_module->release
这三个函数然后分别赋值给 skynet_module 的 create / init / release

snlua.so 的代码在 service_snlua.c
看 snlua_init() 函数代码就知道它将 skynet_context 的 cb 赋值为 _launch

int
snlua_init( struct snlua * l, struct skynet_context * ctx, const char * args) {
     int sz = strlen(args);
     char * tmp = skynet_malloc(sz);
    memcpy(tmp, args, sz);
    skynet_callback(ctx, l , _launch); // 这句代码将 skynet_context 的 cb 赋值为 _launch
    const char * self = skynet_command(ctx, " REG " , NULL);
    uint32_t handle_id = strtoul(self + 1 , NULL, 16 );
     // it must be first message
    skynet_send(ctx, 0 , handle_id, PTYPE_TAG_DONTCOPY, 0 , tmp, sz);
     return 0 ;
}

再看回下面的消息分派 dispatch_message() 里有以下代码, 实际上就是调用了 _launch()
    if (!ctx->cb(ctx, ctx->cb_ud, type, msg->session, msg->source, msg->data, sz)) {
        skynet_free(msg->data);
    }

skynet的启动 2014.11.05

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