os: use the correct constant for P_PID on NetBSD

Dragonfly and FreeBSD both used numerical values for these constants
chosen to be the same as on Solaris. For some reason, NetBSD did not,
and happens to interpret value 0 as P_ALL instead of P_PID
(see https://github.com/NetBSD/src/blob/3323ceb7822f98b3d2693aa26fd55c4ded6d8ba4/sys/sys/idtype.h#L43-L44).

Using the correct value for P_PID should cause wait6 to wait for the
correct process, which may help to avoid the deadlocks reported in

For #50138.
Updates #13987.

Change-Id: I0eacd1faee4a430d431fe48f9ccf837f49c42f39
Reviewed-on: https://go-review.googlesource.com/c/go/+/442478
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Run-TryBot: Bryan Mills <bcmills@google.com>

diff --git a/src/os/wait_wait6.go b/src/os/wait_wait6.go
index 1464576b7cf40f972ddb5c52b3bf2e233136b370..e5cf87b1356f4e03eb7dd9516b81d2f47473cb14 100644 (file)
--- a/src/os/wait_wait6.go
+++ b/src/os/wait_wait6.go
@@ -11,7 +11,10 @@ import (
        "syscall"
 )
 
-const _P_PID = 0
+const (
+       _P_PID        = 0 // everywhere except for NetBSD?
+       _P_PID_NETBSD = 1 // on NetBSD, 0 is P_ALL
+)
 
 // blockUntilWaitable attempts to block until a call to p.Wait will
 // succeed immediately, and reports whether it has done so.
@@ -26,6 +29,8 @@ func (p *Process) blockUntilWaitable() (bool, error) {
                        _, _, errno = syscall.Syscall9(syscall.SYS_WAIT6, _P_PID, uintptr(p.Pid), 0, 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0, 0, 0)
                } else if runtime.GOOS == "freebsd" && runtime.GOARCH == "arm" {
                        _, _, errno = syscall.Syscall9(syscall.SYS_WAIT6, _P_PID, 0, uintptr(p.Pid), 0, 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0, 0)
+               } else if runtime.GOOS == "netbsd" {
+                       _, _, errno = syscall.Syscall6(syscall.SYS_WAIT6, _P_PID_NETBSD, uintptr(p.Pid), 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0)
                } else {
                        _, _, errno = syscall.Syscall6(syscall.SYS_WAIT6, _P_PID, uintptr(p.Pid), 0, syscall.WEXITED|syscall.WNOWAIT, 0, 0)
                }