22.4.6.1 Global Break Condition

In contrast to breaking when execution reaches specified locations, you can also cause a break when a certain event occurs. The global break condition is a condition that is repeatedly evaluated at every stop point. If it evaluates to a non-nil value, then execution is stopped or paused depending on the execution mode, just like a breakpoint. Any errors that might occur as a result of evaluating the condition are ignored, as if the result were nil.

You can set or edit the condition expression, stored in edebug-global-break-condition, using X (edebug-set-global-break-condition).

Using the global break condition is perhaps the fastest way to find where in your code some event occurs, but since it is rather expensive you should reset the condition to nil when not in use.