os: disable the use of netpoll on regular files on *BSDs.
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>
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index 688b68e..c91efa8 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -117,23 +117,29 @@
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
+ }
}
}
