race condition with systemd notification protocol #505

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1. troglobit commented on Sep 14, 2026

   

   troglobit

   on Sep 14, 2026

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   Could you give an example to help me understand? Because often the call to sd_notify(), or pidfile creation, is actually malplaced in the daemon itself.
2. aanderse commented on Sep 15, 2026

   

   aanderse

   on Sep 15, 2026

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   imagine a daemon tries to access NOTIFY_SOCKET before it does anything else... since finit forks the process first it would be possible that the socket isn't bound yet...

   i have a user running systemd-udev in their initramfs and they weren't getting a ready condition for the daemon... we ended up creating a script to test this out...

       #!/bin/sh
       if [ -n "''${NOTIFY_SOCKET:-}" ]; then
         found=
         tries=0
         while [ -z "$found" ] && [ "$tries" -lt 100000 ]; do
           while read -r _ _ _ _ _ _ _ name; do
             if [ "$name" = "$NOTIFY_SOCKET" ]; then
               found=1
               break
             fi
           done < /proc/net/unix
           tries=$((tries + 1))
         done
       fi
       exec "$@"
   

   the command was that script followed by calling udev and this fixed the issue for them

   i ended up creating a vm test to reproduce and was able to... in some cases i got up to 1158 tries before the name appeared

   note that we have only been able to reproduce this in an initramfs so far
3. troglobit commented on Sep 16, 2026

   

   troglobit

   on Sep 16, 2026

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   Aha, got it! I'll see what my friend can make of it while we await review on #500 (stalling my pipeline atm :)

   ❤️React with ❤️3Reacted by Aaron Andersen, Phileas Lebada and deathbymanatee