linux-kernel - Re: [PATCH 5/5] hugetlbfs: Limit wait time when trying to share huge PMD

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Message-ID: <3d98ea00-ea0d-a9b1-9e1a-e78a731c20a5@redhat.com>
Date:   Fri, 13 Sep 2019 14:23:44 -0400
From:   Waiman Long <longman@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [PATCH 5/5] hugetlbfs: Limit wait time when trying to share huge
 PMD

On 9/12/19 5:43 PM, Mike Kravetz wrote:
> On 9/12/19 2:06 AM, Waiman Long wrote:
>> If we can take the rwsem in read mode, that should solve the problem
>> AFAICS. As I don't have a full understanding of the history of that
>> code, I didn't try to do that in my patch.
> Do you still have access to an environment that creates the long stalls?
> If so, can you try the simple change of taking the semaphore in read mode
> in huge_pmd_share.
>
That is what I am planning to do. I don't have an environment to
reproduce the problem myself. I have to create a test kernel and ask the
customer to try it out.

Cheers,
Longman