Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
479 views
in Technique[技术] by (71.8m points)

sockets - Spurious readiness notification for Select System call

On http://linux.die.net/man/2/select, under BUGS section it is mentioned that the select system call may sometimes spuriously set the FD ready and the subsequent read call will return 0. The text describes one such example (wrong checksum) but I am assuming there would be other reasons too (otherwise they would have fixed this).

Any ideas what could the other causes for Select to return a FD ready spuriously.

and does this apply to other OS'es also. I am currently asking about Linux.

Relevant Section for the link above:

Under Linux, select() may report a socket file descriptor as "ready for reading", while nevertheless a subsequent read blocks. This could for example happen when data has arrived but upon examination has wrong checksum and is discarded. There may be other circumstances in which a file descriptor is spuriously reported as ready. Thus it may be safer to use O_NONBLOCK on sockets that should not block.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

This is not exactly an answer, but looking over epoll, these problems seem to be solved for it.

And if I can trust this message in netdev, they at least tried to fix it in poll() and select() too (breaking other things).

Thus, this bug doesn't seem to be relevant in foreseeable future.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...