Change https://go.dev/cl/443066 mentions this issue: os/signal: add missing newlines to TestTerminalSignal

I tried to take a quick look at this on a linux-s390x gomote, but that builder apparently doesn't have strace installed. :(

I tried to take a quick look at this on a linux-s390x gomote, but that builder apparently doesn't have strace installed. :(

@prattmic I've installed strace on all the s390x builders if you can try again

Awesome, thanks. @bcmills was right that the ioctl argument is incorrect (at least on s390x, still waiting on mips buildlet):

1185859 getpgid(0 <unfinished ...>
1185859 <... getpgid resumed>)          = 1185859
1185859 ioctl(3, TIOCSPGRP, [0] <unfinished ...>
1185859 <... ioctl resumed>)            = -1 ESRCH (No such process)

[0] should be [1185859].

Is there an ABI difference for ioctl arguments on s390x? That seems like the most obvious cause, though I don't see evidence of that in ioctl calls in syscall or x/sys or from a quick glance at the Linux source.

I'm going to send a CL to skip this test on s390x for now.

@prattmic it looks like this is an endian issue on s390x. If I cast the pids to int32 it passes for me locally. Not sure if int32 is correct for all platforms this test runs on.

diff --git a/src/os/signal/signal_cgo_test.go b/src/os/signal/signal_cgo_test.go
index 3625637432..086d56a251 100644
--- a/src/os/signal/signal_cgo_test.go
+++ b/src/os/signal/signal_cgo_test.go
@@ -279,7 +279,7 @@ func runSessionLeader(pause time.Duration) {
 		}
 
 		// Take TTY.
-		pgrp := syscall.Getpgrp()
+		pgrp := int32(syscall.Getpgrp())
 		_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, ptyFD, syscall.TIOCSPGRP, uintptr(unsafe.Pointer(&pgrp)))
 		if errno != 0 {
 			return fmt.Errorf("error setting tty process group: %w", errno)
@@ -290,7 +290,7 @@ func runSessionLeader(pause time.Duration) {
 		time.Sleep(pause)
 
 		// Give TTY back.
-		pid := uint64(cmd.Process.Pid)
+		pid := int32(cmd.Process.Pid)
 		_, _, errno = syscall.Syscall(syscall.SYS_IOCTL, ptyFD, syscall.TIOCSPGRP, uintptr(unsafe.Pointer(&pid)))
 		if errno != 0 {
 			return fmt.Errorf("error setting tty process group back: %w", errno)

The code is passing the address of a Go uintptr to a function that takes a pointer to a C int. That will fail on any big-endian 64-bit system. Sent CL 443175.

Change https://go.dev/cl/443175 mentions this issue: os/signal: pass *int32 to ioctl that expects pid_t