socket: avoid exceptions in wrapper code

* ext/socket/lib/socket.rb (Socket.accept_loop): avoid exceptions
  (Socket.udp_server_recv): ditto

Exceptions for common "errors" make debug output noisy and
allocations+backtrace generation hurt performance.
[ruby-core:66385] [ruby-core:69473]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52604 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Tue Nov 17 10:12:30 2015  Eric Wong  <e@80x24.org>
+
+	* ext/socket/lib/socket.rb (Socket.accept_loop): avoid exceptions
+	  (Socket.udp_server_recv): ditto
+
 Tue Nov 17 09:59:00 2015  Eric Wong  <e@80x24.org>
 
 	* ext/socket/ancdata.c (bsock_sendmsg_internal): avoid arg parsing

ext/socket/lib/socket.rb

@@ -792,11 +792,8 @@ class Socket < BasicSocket
     loop {
       readable, _, _ = IO.select(sockets)
       readable.each {|r|
-        begin
-          sock, addr = r.accept_nonblock
-        rescue IO::WaitReadable
-          next
-        end
+        sock, addr = r.accept_nonblock(exception: false)
+        next if sock == :wait_readable
         yield sock, addr
       }
     }
@@ -960,11 +957,8 @@ class Socket < BasicSocket
   #
   def self.udp_server_recv(sockets)
     sockets.each {|r|
-      begin
-        msg, sender_addrinfo, _, *controls = r.recvmsg_nonblock
-      rescue IO::WaitReadable
-        next
-      end
+      msg, sender_addrinfo, _, *controls = r.recvmsg_nonblock(exception: false)
+      next if msg == :wait_readable
       ai = r.local_address
       if ai.ipv6? and pktinfo = controls.find {|c| c.cmsg_is?(:IPV6, :PKTINFO) }
         ai = Addrinfo.udp(pktinfo.ipv6_pktinfo_addr.ip_address, ai.ip_port)