Re: [PATCH rdma-next v1 4/6] IB/core: Fix use workqueue without WQ_MEM_RECLAIM

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Mon, Oct 16, 2017 at 01:24:12PM -0400, Jonathan Toppins wrote:
> On 10/16/2017 01:45 AM, Leon Romanovsky wrote:
> > From: Parav Pandit <parav-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >
> > The IB/core provides address resolution service and invokes callback
> > handler when address resolve request completes of requester in worker
> > thread context.
> >
> > Such caller might allocate or free memory in callback handler
> > depending on the completion status to make further progress or to
> > terminate a connection. Most ULPs resolve route which involves
> > allocating route entry and path record elements in callback event handler.
> >
> > It has been noticed that WQ_MEM_RECLAIM flag should not be used for
> > workers that tend to allocate memory in this [1] thread discussion.
> >
> > In order to mitigate this situation, WQ_MEM_RECLAIM flag was dropped for
> > other such WQs in this [2] patch.
> >
> > Similar problem might arise with address resolution path, though its not
> > yet noticed. The ib_addr workqueue is not memory reclaim path due to its
> > nature of invoking callback that might allocate memory or don't free any
> > memory under memory pressure.
> >
> > [1] https://www.spinics.net/lists/linux-rdma/msg53239.html
> > [2] https://www.spinics.net/lists/linux-rdma/msg53416.html
> >
> > Fixes: f54816261c2b ("IB/addr: Remove deprecated create_singlethread_workqueue")
> > Fixes: 5fff41e1f89d ("IB/core: Fix race condition in resolving IP to MAC")
> > Signed-off-by: Parav Pandit <parav-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > Reviewed-by: Daniel Jurgens <danielj-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > Signed-off-by: Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
>
> This looks like a -stable patch candidate. Once accepted this should
> probably be queued for v4.9+.

I don't have any strong opinion about that.

Thanks

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