My understanding currently is sudo sets up a signal handler in pre_exec and another signal handler later on which is tied into its main event loop. Go gets initialized when the pre_exec signal handler is used and it adds rt_sigaction(SIGCHLD..) with the SA_ONSTACK flag as mentioned here <https://pkg.go.dev/os/signal#hdr-Non_Go_programs_that_call_Go_code>. Then after the sudo command (echo) gets executed, the SIGCHLD is received by one of the go threads which then runs the pre_exec signal handler which is the old and nonexistent signal handler.
My approach is to block the Go threads from receiving the SIGCHLD signal and thus not let the signal to be handled by the old signal handler. On Friday, August 11, 2023 at 10:05:48 PM UTC-7 Ian Lance Taylor wrote: > On Fri, Aug 11, 2023 at 11:51 AM Chandrasekhar R <crama...@gmail.com> > wrote: > > > > I am planning on using a pam module written in Go (specifically > https://github.com/uber/pam-ussh) . When I run a script which calls sudo > continuously with an echo command, I am noticing zombie/defunct processes > starting to pop up. > > > > On doing strace, I noticed that the SIGCHLD gets delivered to one of the > threads created when Go gets initialized (i.e. the shared object gets > loaded). > > > > I tried to add one level of indirection by having a separate C code > which creates a new thread, sets the signal mask to block SIGCHLD and then > use dlopen to open the shared object created using cgo. I am still facing > the same issue, is there any pointer on how to fix this issue? I think this > would be a wide issue across all PAM modules written using cgo. > > As far as I know the specific thread that receives a SIGCHLD signal is > fairly random. What matters is not the thread that receives the > signal, but the signal handler that is installed. Signal handlers are > process-wide. What signal handler is running when you get a SIGCHLD? > What signal handler do you expect to run? > > Ian > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/7b395394-da12-4b19-9e07-5c8f7e91dcabn%40googlegroups.com.
