linux-kernel - Re: [HMM 12/15] mm/migrate: new memory migration helper for use with device memory v4

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Date:   Thu, 13 Jul 2017 22:32:03 -0700
From:   Evgeny Baskakov <ebaskakov@...dia.com>
To:     Jerome Glisse <jglisse@...hat.com>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        John Hubbard <jhubbard@...dia.com>,
        David Nellans <dnellans@...dia.com>,
        Mark Hairgrove <mhairgrove@...dia.com>,
        Sherry Cheung <SCheung@...dia.com>,
        Subhash Gutti <sgutti@...dia.com>
Subject: Re: [HMM 12/15] mm/migrate: new memory migration helper for use with
 device memory v4

On 7/13/17 1:16 PM, Jerome Glisse wrote:

> I updated hmm-next with a patch that might fix some other issues but i am
> still trying to get this dead lock you are seing. Does it happens quickly
> with the test program ?
>
> I can't see how it dead lock on the page lock bit. Going over and over all
> code path we always unlock page once we are done or when we back off from
> migration. So far i haven't been able to reproduce thought i haven't had
> much time to test as other thing kept me busy. I should be back looking into
> that tomorrow.
>
> https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-next
>
> Cheers,
> Jérôme

Hi Jerome,

The issue persists in the updated hmm-next. The test program hangs on 
the first run on my 12-core SMT system:

$ sudo ./run.sh
&&& 2 migrate threads, 2 read threads: STARTING
&&& 2 migrate threads, 2 read threads: PASSED
&&& 2 migrate threads, 3 read threads: STARTING
&&& 2 migrate threads, 3 read threads: PASSED
&&& 2 migrate threads, 4 read threads: STARTING
&&& 2 migrate threads, 4 read threads: PASSED
&&& 3 migrate threads, 2 read threads: STARTING
....
[no progress being made]

Please find attached a new kernel log with blocked tasks shown and my 
kernel config. I hope that is helpful.

Thanks,

-- 
Evgeny Baskakov
NVIDIA



View attachment "config" of type "text/plain" (117855 bytes)

View attachment "kernel.log" of type "text/plain" (8602 bytes)