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If a server A is deleted while a stats dump is currently on it, deletion is delayed thanks to reference counting. Server A is nonetheless removed from the proxy list. However, this list is a single linked list. If the next server B is deleted and freed immediately, server A would still point to it. This problem has been solved by the prev_deleted list in servers. This model seems correct, but it is difficult to ensure completely its validity. In particular, it implies when stats dump is resumed, server A elements will be accessed despite the server being in a half-deleted state. Thus, it has been decided to completely ditch the refcount mechanism for stats dump. Instead, use the watcher element to register every stats dump currently tracking a server instance. Each time a server is deleted on the CLI, each stats dump element which may points to it are updated to access the next server instance, or NULL if this is the last server. This ensures that a server which was deleted via CLI but not completely freed is never accessed on stats dump resumption. Currently, no race condition related to dynamic servers and stats dump is known. However, as described above, the previous model is deemed too fragile, as such this patch is labelled as bug-fix. It should be backported up to 2.6, after a reasonable period of observation. It relies on the following patch : MINOR: list: define a watcher type