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os: disable the use of netpoll on regular files on *BSDs.

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The kqueue based netpoller always registers file descriptors with EVFILT_READ and EVFILT_WRITE.
However only EVFILT_READ notification is supported for regular files.
On FreeBSD a regular file is always reported as ready for writing, resulting in a busy wait.
On Darwin, Dragonfly, NetBSD and OpenBSD, a regular file is reported as ready for both reading and writing only once.

Updates #19093

Change-Id: If284341f60c6c2332fb5499637d4cfa7a4e26b7b
Reviewed-on: https://go-review.googlesource.com/c/156379
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Yuval Pavel Zholkover 2019-01-07 02:06:38 +02:00 committed by Ian Lance Taylor
parent 9473c044f1
commit 79c50c4d57
1 changed files with 19 additions and 13 deletions
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32
src/os/file_unix.go
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@ -117,23 +117,29 @@ func newFile(fd uintptr, name string, kind newFileKind) *File {
pollable := kind == kindOpenFile || kind == kindPipe || kind == kindNonBlock
// Don't try to use kqueue with regular files on FreeBSD.
// It crashes the system unpredictably while running all.bash.
// Issue 19093.
// If the caller passed a non-blocking filedes (kindNonBlock),
// we assume they know what they are doing so we allow it to be
// used with kqueue.
if runtime.GOOS == "freebsd" && kind == kindOpenFile {
pollable = false
}
// On Darwin, kqueue does not work properly with fifos:
// closing the last writer does not cause a kqueue event
// for any readers. See issue #24164.
if runtime.GOOS == "darwin" && kind == kindOpenFile {
if kind == kindOpenFile {
var st syscall.Stat_t
if err := syscall.Fstat(fdi, &st); err == nil && st.Mode&syscall.S_IFMT == syscall.S_IFIFO {
pollable = false
switch runtime.GOOS {
// Don't try to use kqueue with regular files on *BSDs.
// on FreeBSD with older kernels it used to crash the system unpredictably while running all.bash.
// while with newer kernels a regular file is always reported as ready for writing.
// on Dragonfly, NetBSD and OpenBSD the fd is signaled only once as ready (both read and write).
// Issue 19093.
case "dragonfly", "freebsd", "netbsd", "openbsd":
if err := syscall.Fstat(fdi, &st); err == nil && st.Mode&syscall.S_IFMT == syscall.S_IFREG {
pollable = false
}
case "darwin":
// In addition to the behavior described above for regular files,
// on Darwin, kqueue does not work properly with fifos:
// closing the last writer does not cause a kqueue event
// for any readers. See issue #24164.
if err := syscall.Fstat(fdi, &st); err == nil && (st.Mode&syscall.S_IFMT == syscall.S_IFIFO || st.Mode&syscall.S_IFMT == syscall.S_IFREG) {
pollable = false
}
}
}