<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\documentclass[crop,tikz]{standalone}
\usetikzlibrary{arrows.meta, backgrounds, positioning, fit, petri}
\begin{document}
\begin{tikzpicture}[
  auto,
  node distance=1.3cm,
  on grid,
  &gt;={Stealth[round]},
  bend angle=45,
  every place/.style={minimum size=6mm, thick, draw=blue!75, fill=blue!20},
  every transition/.style={thick, draw=black!75, fill=black!20}
]
  \node[place, tokens=5] (waiting)                       {};
  \node[place] (critical)  [below=of waiting]  {};
  \node[place] (semaphore) [below=of critical] {};
  \node[transition] (leave critical) [right=of critical] {}
    edge[pre]                      (critical)
    edge[post] node[auto,swap] {2} (waiting)
    edge[pre]                      (semaphore);
  \node[transition] (enter critical) [left=of critical] {}
    edge[post] (critical)
    edge[pre]  (waiting)
    edge[post] (semaphore);
  \begin{scope}[on background layer]
    \node[fill=black!25, fit=(waiting) (critical) (semaphore) (leave critical) (enter critical)] {};
  \end{scope}
\end{tikzpicture}
\end{document}
</pre></body></html>