Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> Jan Kiszka wrote:
>>>> Hi Gilles,
>>>>
>>>> trying to understand the cb_read/write lock usage, some question came up
>>>> here: What prevents that the mutexq iteration in pse51_mutex_check_init
>>>> races against pse51_mutex_destroy_internal?
>>>>
>>>> If nothing, then I wonder if we actually have to iterate over the whole
>>>> queue to find out whether a given object has been initialized and
>>>> registered already or not. Can't this be encoded differently?
>>> We actually iterate over the queue only if the magic happens to be
>>> correct, which is not the common case.
>> However, there remains a race window with other threads removing other
>> mutex objects in parallel, changing the queue - risking a kernel oops.
>> And that is what worries me. It's unlikely. but possible. It's unclean.
> 
> Ok. This used to be protected by the nklock. We should add the nklock again.

Well I do not think that anyone is rescheduling, so we could probably
replace the nklock with a per-kqueue xnlock.

-- 
                                            Gilles.

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