netdev - Re: [RFC rdma-next] RDMA/core: Add attribute WQ_MEM

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Message-ID: <20200218153156.GD31668@ziepe.ca>
Date:   Tue, 18 Feb 2020 11:31:56 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lang Cheng <chenglang@...wei.com>
Cc:     dledford@...hat.com, leon@...nel.org, davem@...emloft.net,
        salil.mehta@...wei.com, yisen.zhuang@...wei.com,
        linuxarm@...wei.com, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org
Subject: Re: [RFC rdma-next] RDMA/core: Add attribute WQ_MEM_RECLAIM to
 workqueue "infiniband"

On Tue, Feb 18, 2020 at 11:35:35AM +0800, Lang Cheng wrote:
> The hns3 driver sets "hclge_service_task" workqueue with
> WQ_MEM_RECLAIM flag in order to guarantee forward progress
> under memory pressure.

Don't do that. WQ_MEM_RECLAIM is only to be used by things interlinked
with reclaimed processing.

Work on queues marked with WQ_MEM_RECLAIM can't use GFP_KERNEL
allocations, can't do certain kinds of sleeps, can't hold certain
kinds of locks, etc.

Jason