Confirming that: signal (SIGCHLD, SIG_DFL);
works. Thank you, Rich! Best Regards, Peter On Thu, Nov 8, 2018 at 5:07 PM Richard W.M. Jones <rjo...@redhat.com> wrote: > On Thu, Nov 08, 2018 at 04:51:31PM +0200, Peter Dimitrov wrote: > > Here are strace outputs per process. > > > > strace_output.22076 is the plugin's pid. (A little before forking) > > Ah ha. > > Close reading of the waitpid(2) man page says: > > ECHILD (for waitpid() or waitid()) The process specified by pid > (wait‐ > pid()) or idtype and id (waitid()) does not exist or is > not a > child of the calling process. (This can happen for one's > own > child if the action for SIGCHLD is set to SIG_IGN. See also > the > Linux Notes section about threads.) > > I'm going to guess that collectd is leaking the signal handler setting > into the child process instead of resetting it. This is a bug in > collectd. > > It's surprisingly hard to correctly fork a process in Unix. Here's > what libvirt does, which is the most comprehensive code that I know > of. It involves resetting multiple things before running the child: > > > https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/util/vircommand.c;h=de937f6f9aa91abb518eac98bfac9dcf37e1f5df;hb=HEAD#l280 > > While you're getting the collectd bug fixed, the easiest workaround is > probably to add: > > signal (SIGCHLD, SIG_DFL); > > in your code. > > Rich. > > -- > Richard Jones, Virtualization Group, Red Hat > http://people.redhat.com/~rjones > Read my programming and virtualization blog: http://rwmj.wordpress.com > virt-top is 'top' for virtual machines. Tiny program with many > powerful monitoring features, net stats, disk stats, logging, etc. > http://people.redhat.com/~rjones/virt-top >
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