Hallvard B Furuseth wrote:

hyc@symas.com writes:

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slapd/cancel.c sets o_abandon before o_cancel. Thus it's possible for the canceled operation to obey o_abandon before o_cancel gets set.

Cancel is just best-effort, why not just set o_cancel before o_abandon?

Memory coherence. Without mutex protection, the cancelled thread might still see the o_abandon change before the o_cancel change. And thus not send a response, nor update info for the Cancel operation to react to.

I'd prefer to condense it all into a bitfield. We already ensure that the c_mutex is held when setting these flags. It would be a lot of overhead to grab the mutex just to read the flag, and would require additional analysis to make sure the new locking behavior doesn't introduce new deadlocks.