[lttng-dev] [PATCH lttng-ust 2/8] Fix: missing event removal from the event hashtable

[Mathieu Desnoyers]

----- On Feb 8, 2018, at 3:42 PM, Francis Deslauriers francis.deslauriers at efficios.com wrote:

> 2018-02-07 15:50 GMT-05:00 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>:
>>
>>
>> ----- On Feb 2, 2018, at 2:48 PM, Francis Deslauriers
>> francis.deslauriers at efficios.com wrote:
>>
>> Is this really a fix ? Or is it a preparation step in order to be able to
>> remove events before the end of the session lifetime ?
> 
> It's not a fix in the sense that it was not causing issues because it
> was only called at session destruction.
> But it's a fix in the sense that the _lttng_event_destroy function was
> not doing all the work necessary to destroy an event passed as
> argument. Taken by itself, a call to this function would leave one of
> the hlists of the hash table in a incorrect state by freeing an
> element without cds_hlist_del() it from the hlist before.
> 
> That was my thought process. What do you think?

A fix is something I need to backport to make things work. I don't see
this as a fix based on that definition.

Thanks,

Mathieu

> 
> Thank you,
> Francis
> 
>> Thanks,
>>
>> Mathieu
>>
>>
>>> Signed-off-by: Francis Deslauriers <francis.deslauriers at efficios.com>
>>> ---
>>> liblttng-ust/lttng-events.c | 4 ++++
>>> 1 file changed, 4 insertions(+)
>>>
>>> diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c
>>> index f4a7ccc..7419f78 100644
>>> --- a/liblttng-ust/lttng-events.c
>>> +++ b/liblttng-ust/lttng-events.c
>>> @@ -883,7 +883,11 @@ void _lttng_event_destroy(struct lttng_event *event)
>>> {
>>>       struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
>>>
>>> +     /* Remove from event list. */
>>>       cds_list_del(&event->node);
>>> +     /* Remove from event hash table. */
>>> +     cds_hlist_del(&event->hlist);
>>> +
>>>       lttng_destroy_context(event->ctx);
>>>       lttng_free_event_filter_runtime(event);
>>>       /* Free event enabler refs */
>>> --
>>> 2.7.4
>>
>> --
>> Mathieu Desnoyers
>> EfficiOS Inc.
>> http://www.efficios.com
> 
> 
> 
> --
> Francis Deslauriers
> Software developer
> EfficiOS inc.

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com