Make update read_offset_ atomic
Make update read_offset_ atomic

yvxiang/dfs,baidu/bfs,bluebore/dfs,yvxiang/coverage_for_bfs,bluebore/dfs,myawan/bfs-1,myawan/bfs-1,lylei/dfs,myawan/bfs-1,linyvxiang/dfs,yvxiang/dfs,linyvxiang/dfs,yvxiang/dfs,baidu/bfs,baidu/bfs,lylei/dfs,imotai/bfs,yvxiang/coverage_for_bfs,yvxiang/dfs,myawan/bfs-1,yvxiang/coverage_for_bfs,00k/ToyDFS,imotai/bfs,lylei/dfs,yvxiang/coverage_for_bfs,linyvxiang/dfs,bluebore/bfs,bluebore/bfs,lylei/dfs,bluebore/dfs,imotai/bfs,bluebore/bfs,baidu/bfs,00k/ToyDFS