This renderer for CommandButtons will disable the button while an Ajax action is being processed.

To enable this renderer, in the faces-config.xml, in the <render-kit>...</render-kit> section, add:

<renderer>
    <component-family>org.primefaces.component</component-family>
    <renderer-type>org.primefaces.component.CommandButtonRenderer</renderer-type>
    <renderer-class>org.primefaces.extensions.renderer.CommandButtonSingleClickRenderer</renderer-class>
</renderer>

Demo:

Sleep 2 seconds

Confirm dialog and sleep 2 seconds

Confirm popup and sleep 2 seconds