os/signal: not all notifications about SIGCHLD are sent

[noxiouz]

1. What version of Go are you using (go version)?

go version go1.6.2 darwin/amd64

Also it's cross compiled and tested on Linux

1. What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/noxiouz/Go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GO15VENDOREXPERIMENT="1"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fno-common"
CXX="clang++"
CGO_ENABLED="1"

1. What did you do?
   http://play.golang.org/p/lLTgaA8MRo
2. What did you expect to see?
   Get notification about SIGCHLD from every child
3. What did you see instead?
   Only 65-72 notifications are sent in average case

sigchld watcher is ready
10 sec without SIGCHLD. Got 72

[ianlancetaylor]

I haven't checked yet, but doesn't the same thing happen in a C program? Except for the real time signals, Unix systems do not normally ensure that all instances of a signal are delivered. If a signal is raised twice before the program has a chance to handle the first raised signal, the signal handler is only invoked once.

[noxiouz]

Unfortunately, I am not an expert in Unix signals sphere. So if it's a planned behavior, the issue can be closed, of course.

[noxiouz]

Yes, I found http://www.gnu.org/software/libc/manual/html_node/Merged-Signals.html#Merged-Signals
Thanks! At least, now I know.