Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 7 Apr 2020 09:35:20 -0400
From:   Tejun Heo <tj@kernel.org>
To:     Qais Yousef <qais.yousef@arm.com>
Cc:     Qian Cai <cai@lca.pw>, Prateek Sood <prsood@codeaurora.org>,
        Li Zefan <lizefan@huawei.com>, cgroups@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: Deadlock due to "cpuset: Make cpuset hotplug synchronous"
Message-ID: <20200407133520.GI162390@mtj.duckdns.org>
References: <F0388D99-84D7-453B-9B6B-EEFF0E7BE4CC@lca.pw>
 <20200325191922.GM162390@mtj.duckdns.org>
 <20200326101529.xh763j5frq2r7mqv@e107158-lin>
 <20200403145523.GC162390@mtj.duckdns.org>
 <20200406105522.c66p4vzzzylety5d@e107158-lin.cambridge.arm.com>
 <20200406143405.GH162390@mtj.duckdns.org>
 <20200407130725.jhtth3bneo33zex6@e107158-lin.cambridge.arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200407130725.jhtth3bneo33zex6@e107158-lin.cambridge.arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Apr 07, 2020 at 02:07:26PM +0100, Qais Yousef wrote:
> On 04/06/20 10:34, Tejun Heo wrote:
> > On Mon, Apr 06, 2020 at 11:55:23AM +0100, Qais Yousef wrote:
> > > What would be the right approach to get a fix in then? We have been skipping
> > > this test for a while and we'd like to enable it but this failure is a
> > > blocking issue.
> > 
> > Update the test so that it accounts for the async nature of the operation?
> 
> With a sleep() between the hp ops and the read? Isn't this a nasty hack?

Some operations are just async. Why is that inherently wrong?

> I was just trying to find out what can be done for 5.7. But based on your
> response this is sadly a dead end. For no reason I can comprehend.

Because it's creating real issues while trying to address a non-real problem.
It's dumb. Fix the non-real part.

Thanks.

-- 
tejun