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It is common to close network connection while another goroutine is blocked reading on another goroutine. This sequence corresponds to windows calls to WSARecv to start io, followed by GetQueuedCompletionStatus that blocks until io completes, and, finally, closesocket called from another thread. We were expecting that closesocket would unblock GetQueuedCompletionStatus, and it does, but not always (http://code.google.com/p/go/issues/detail?id=4170#c5). Also that sequence results in connection is being reset. This CL inserts CancelIo between GetQueuedCompletionStatus and closesocket, and waits for both WSARecv and GetQueuedCompletionStatus to complete before proceeding to closesocket. This seems to fix both connection resets and issue 4170. It also makes windows code behave similar to unix version. Unfortunately, CancelIo needs to be called on the same thread as WSARecv. So we have to employ strategy we use for connections with deadlines to every connection now. It means, there are 2 unavoidable thread switches for every io. Some newer versions of windows have new CancelIoEx api that doesn't have these drawbacks, and this CL uses this capability when available. As time goes by, we should have less of CancelIo and more of CancelIoEx systems. Computers with CancelIoEx are also not affected by issue 4195 anymore. Fixes #3710 Fixes #3746 Fixes #4170 Partial fix for issue 4195 R=golang-dev, mikioh.mikioh, bradfitz, rsc CC=golang-dev https://golang.org/cl/6604072 |
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This is the source code repository for the Go programming language. For documentation about how to install and use Go, visit http://golang.org/ or load doc/install.html in your web browser. After installing Go, you can view a nicely formatted doc/install.html by running godoc --http=:6060 and then visiting http://localhost:6060/doc/install.html. Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file. -- Binary Distribution Notes If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this README). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install.html). You should also add the Go binary directory $GOROOT/bin to your shell's path. For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile: export GOROOT=$HOME/go export PATH=$PATH:$GOROOT/bin See doc/install.html for more details.