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    SubjectRe: Deadlock due to "cpuset: Make cpuset hotplug synchronous"
    On 04/03/20 10:55, Tejun Heo wrote:
    > On Thu, Mar 26, 2020 at 10:15:32AM +0000, Qais Yousef wrote:
    > > On 03/25/20 15:19, Tejun Heo wrote:
    > > > On Wed, Mar 25, 2020 at 03:16:56PM -0400, Qian Cai wrote:
    > > > > The linux-next commit a49e4629b5ed (“cpuset: Make cpuset hotplug synchronous”)
    > > > > introduced real deadlocks with CPU hotplug as showed in the lockdep splat, since it is
    > > > > now making a relation from cpu_hotplug_lock —> cgroup_mutex.
    > > >
    > > > Prateek, can you please take a look? Given that the merge window is just around
    > > > the corner, we might have to revert and retry later if it can't be resolved
    > > > quickly.
    > >
    > > I've ran cpuset_hotplug and cpuhotplug LTP tests using next-20200325 but
    > > couldn't reproduce it.
    > >
    > > Hopefully that can be fixed, but if you had to revert it, do you mind picking
    > > this instead to fix the LTP issue I encountered before?
    > >
    > > https://lore.kernel.org/lkml/20200211141554.24181-1-qais.yousef@arm.com/
    >
    > So, I'd rather not, for now anyway. It isn't a real problem and I don't wanna
    > add a wait vector there.

    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.

    Android relies on cpuset and some devices use hotplug to manage thermal/power.
    So it's an interesting combination to be able to test for us.

    Thanks

    --
    Qais Yousef

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