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Subject: Re: [PATCH 5/5] hugetlbfs: Limit wait time when trying to share huge
 PMD
To:     Mike Kravetz <mike.kravetz@oracle.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Will Deacon <will.deacon@arm.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, Davidlohr Bueso <dave@stgolabs.net>
References: <20190911150537.19527-1-longman@redhat.com>
 <20190911150537.19527-6-longman@redhat.com>
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 <b7d7d109-03cf-d750-3a56-a95837998372@redhat.com>
 <87ac9e4f-9301-9eb7-e68b-a877e7cf0384@oracle.com>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <3d98ea00-ea0d-a9b1-9e1a-e78a731c20a5@redhat.com>
Date:   Fri, 13 Sep 2019 14:23:44 -0400
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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