Thanks Kurtis for the reply. I understand defunct process mechanism.
As I mentioned in the initial mail, [Correct me if I am wrong here], In a
process if there is main thread and a detached thread created by main
thread, when the main thread exits the process is kept in defunct state,
since the created thread is still
executing, I was thinking if we have such scenario in go runtime. That
could be the reason I see this thread is waiting on futex and holding the
file handles and causing the go process (kernel) not to send SIGCHLD to
parent process.
For example below case
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>
void *thread_function(void *args)
{
printf("The is new thread! Sleep 20 seconds...\n");
sleep(100);
printf("Exit from thread\n");
pthread_exit(0);
}
int main(int argc, char **argv)
{
pthread_t thrd;
pthread_attr_t attr;
int res = 0;
res = pthread_attr_init(&attr);
res = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
res = pthread_create(&thrd, &attr, thread_function, NULL);
res = pthread_attr_destroy(&attr);
printf("Main thread. Sleep 5 seconds\n");
sleep(5);
printf("Exit from main process\n");
pthread_exit(0);
}
ujonnala@ ~/mycode/go () $ ps -T
PID SPID TTY TIME CMD
43635 43635 pts/29 00:00:00 a.out <defunct>
43635 43638 pts/29 00:00:00 a.out
Due to the detached thread still executing the process left in defunt
state.
Thanks for checking on this, I will see if we can reproduce my situation on
a newer kernel.
Thanks & Regards,
Uday Kiran
On Thursday, September 10, 2020 at 9:49:06 PM UTC-7 Kurtis Rader wrote:
> On Thu, Sep 10, 2020 at 9:25 PM Uday Kiran Jonnala <juday...@gmail.com>
> wrote:
>
>> Thanks for the reply. We are fixing the issue. But the point I wanted to
>> bring it up here is the issue of a thread causing the go process to be in
>> defunct state.
>>
>
> Any thread can cause the go process to enter the "defunct" state. For
> example, by calling os.Exit(), or panic(), or causing a signal to be
> delivered that terminates the process (e.g., SIGSEGV).
>
>
>> My kernel version is
>> Linux version 4.14.175-1.nutanix.20200709.el7.x86_64 (dev@ca4b0551898c)
>> (gcc version 7.3.1 20180303 (Red Hat 7.3.1-5) (GCC)) #1 SMP Fri Jul 10
>> 02:17:54 UTC 2020
>>
>
> Is that the output of `uname -a`? It seems to suggest you're using CentOS
> provided by the https://www.nutanix.com/go/linux-on-ahv cloud
> environment. So we've established you are using Linux with kernel version
> 4.14. A kernel that is now three years old. I don't have anything like it
> installed on any of my virtual machines so I can't explore how it handles
> defunct processes. But my prior point stands: A "defunct" process is one
> that has been terminated but whose parent process has not reaped its exit
> status. Either that parent process has a bug (the most likely explanation)
> or your OS has a bug.
>
> --
> Kurtis Rader
> Caretaker of the exceptional canines Junior and Hank
>
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