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

[Francis Deslauriers]

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?

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.