linux-kernel - Re: [RFC] net/mlx5_core/en_main: Remove deprecated create

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Message-ID: <20160729122516.GH2542@mtj.duckdns.org>
Date:	Fri, 29 Jul 2016 08:25:16 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Saeed Mahameed <saeedm@....mellanox.co.il>
Cc:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>,
	Saeed Mahameed <saeedm@...lanox.com>,
	Matan Barak <matanb@...lanox.com>,
	Leon Romanovsky <leonro@...lanox.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	linux-rdma@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] net/mlx5_core/en_main: Remove deprecated create_workqueue

Hello,

On Fri, Jul 29, 2016 at 01:30:05AM +0300, Saeed Mahameed wrote:
> > Are the workitems being used on a memory reclaim path?
> 
> do you mean they need to allocate memory ?

It's a bit convoluted.  A workqueue needs WQ_MEM_RECLAIM flag to be
guaranteed forward progress under memory pressure, so any workqueue
which may be depended upon during memory reclaim should have the flag
set; otherwise, the system can deadlock (try to reclaim memory, hits
the wq which can't make forward progress due to lack of memory).  For
network devices, the requirement comes from block-over-network or nfs
which can be involved in memory reclaim.

Thanks.

-- 
tejun