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

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Message-ID: <87ac9e4f-9301-9eb7-e68b-a877e7cf0384@oracle.com>
Date:   Thu, 12 Sep 2019 09:43:27 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Waiman Long <longman@...hat.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 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.

-- 
Mike Kravetz