linux环境下loopCloseConn引起的panic

[hihaha]

Linux环境下使用gnet遇到如下panic，
OnClosed, ts:2020-07-08 15:14:45.124678462 +0800 CST m=+19.847459851, cnn:0xc0002f2000
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x38 pc=0x68fad0]

goroutine 530 [running]:
github.com/panjf2000/gnet/ringbuffer.(*RingBuffer).IsEmpty(...)
github.com/panjf2000/gnet/ringbuffer/ring_buffer.go:372
github.com/panjf2000/gnet.(*eventloop).loopCloseConn(0xc0002a6000, 0xc0002f2000, 0x0, 0x0, 0x0, 0xf)
github.com/panjf2000/gnet/eventloop_unix.go:193 +0x30
github.com/panjf2000/gnet.(*conn).Close.func1(0x0, 0x0)
github.com/panjf2000/gnet/connection_unix.go:234 +0x3b
github.com/panjf2000/gnet/internal.(*AsyncJobQueue).ForEach(0xc000290028, 0xc000292000, 0x8)
github.com/panjf2000/gnet/internal/queue.go:56 +0xae
github.com/panjf2000/gnet/internal/netpoll.(*Poller).Polling(0xc000290000, 0xc00017df78, 0x0, 0x0)
github.com/panjf2000/gnet/internal/netpoll/epoll.go:112 +0x29e
github.com/panjf2000/gnet.(*server).activateSubReactor(0xc000164090, 0xc0002a6000)
github.com/panjf2000/gnet/reactor_linux.go:50 +0xb1
github.com/panjf2000/gnet.(*server).startSubReactors.func1.1(0xc000164090, 0xc0002a6000)
github.com/panjf2000/gnet/server_unix.go:91 +0x35
created by github.com/panjf2000/gnet.(*server).startSubReactors.func1
github.com/panjf2000/gnet/server_unix.go:90 +0x6a

产生这个panic的原因：异步多goroutine对conn操作，conn先Close, 后续又另一个AsycWrite，再进入函数
func (el *eventloop) loopCloseConn(c *conn, err error) 时，conn已经被release了，
if !c.outboundBuffer.IsEmpty() && err == nil {
_ = el.loopWrite(c)
}
上面if的判断中c.outboundBuffer 已经是nil，所以发生了panic。

修正建议， 将判断outboundBuffer是否为空的逻辑下移到判断conn是否opened的后面。

--- a/src/github.com/panjf2000/gnet/eventloop_unix.go
+++ b/src/github.com/panjf2000/gnet/eventloop_unix.go
@@ -190,15 +190,15 @@ func (el *eventloop) loopWrite(c *conn) error {
 }

 func (el *eventloop) loopCloseConn(c *conn, err error) error {
-       if !c.outboundBuffer.IsEmpty() && err == nil {
-               _ = el.loopWrite(c)
-       }
-
        if !c.opened {
                el.svr.logger.Debugf("The fd=%d in event-loop(%d) is already closed, skipping it", c.fd, el.idx)
                return nil
        }

+       if !c.outboundBuffer.IsEmpty() && err == nil {
+               _ = el.loopWrite(c)
+       }
+
        err0, err1 := el.poller.Delete(c.fd), unix.Close(c.fd)
        if err0 == nil && err1 == nil {
                delete(el.connections, c.fd)

[panjf2000]

Nice catch! @hihaha

有兴趣提个 PR 修复吗？

[hihaha]

Nice catch! @hihaha

有兴趣提个 PR 修复吗？

可以的

[panjf2000]

@hihaha
今天能够提交 PR 吗？这只是个小改动，我想尽快修复，如果你没时间的话我就自己修复了。