tree 8e2f1c94883410fae135d037db114be98a0aa8f7
parent d4c80d19a80cbdf946102f3b787ce23bf95e4e12
author Dmitriy Vyukov <dvyukov@google.com> 1363856059 +0400
committer Dmitriy Vyukov <dvyukov@google.com> 1363856059 +0400
golang-hg ff779e477085318a7917891f04413596059541c7

runtime: explicitly remove fd's from epoll waitset before close()
Fixes #5061.

Current code relies on the fact that fd's are automatically removed from epoll set when closed. However, it is not true. Underlying file description is removed from epoll set only when *all* fd's referring to it are closed.

There are 2 bad consequences:
1. Kernel delivers notifications on already closed fd's.
2. The following sequence of events leads to error:
   - add fd1 to epoll
   - dup fd1 = fd2
   - close fd1 (not removed from epoll since we've dup'ed the fd)
   - dup fd2 = fd1 (get the same fd as fd1)
   - add fd1 to epoll = EEXIST

So, if fd can be potentially dup'ed of fork'ed, it's necessary to explicitly remove the fd from epoll set.

R=golang-dev, bradfitz, dave
CC=golang-dev
https://golang.org/cl/7870043