04/12/2018 13:22, Anatoly Burakov:
> Currently, malloc statistics and external heap creation code
> use memory hotplug lock as a way to synchronize accesses to
> heaps (as in, locking the hotplug lock to prevent list of heaps
> from changing under our feet). At the same time, malloc
> statistics code will also lock the heap because it needs to
> access heap data and does not want any other thread to allocate
> anything from that heap.
>
> In such scheme, it is possible to enter a deadlock with the
> following sequence of events:
>
> thread 1 thread 2
> rte_malloc()
> rte_malloc_dump_stats()
> take heap lock
> take hotplug lock
> failed to allocate,
> attempt to take
> hotplug lock
> attempt to take heap lock
>
> Neither thread will be able to continue, as both of them are
> waiting for the other one to drop the lock. Adding an
> additional lock will require an ABI change, so instead of
> that, make malloc statistics calls thread-unsafe with
> respect to creating/destroying heaps.
>
> Fixes: 72cf92b31855 ("malloc: index heaps using heap ID rather than NUMA
> node")
> Cc: sta...@dpdk.org
>
> Signed-off-by: Anatoly Burakov <anatoly.bura...@intel.com>
> ---
>
> Notes:
> IMO this is the best we can do for 18.11 without breaking ABI.
> For 19.02, we can introduce a new global heap lock (something
> i should've done in the first place...), so this patch is
> not applicable to 19.02. For 19.02, we can fix this properly
> by introducing another lock and breaking the EAL ABI.
>
> Not sure where to put docs update, feedback welcome.
This patch is also changing the API, because functions become not thread-safe.
I think you should note it in the release notes.
About 19.02, do we want to take this patch (with release notes updated)?
