From: Michal Hocko <mhocko@kernel.org>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Waiman Long <longman@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
aneesh.kumar@linux.ibm.com
Subject: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue
Date: Mon, 16 Dec 2019 14:37:11 +0100 [thread overview]
Message-ID: <20191216133711.GH30281@dhcp22.suse.cz> (raw)
In-Reply-To: <20191212190427.ouyohviijf5inhur@linux-p48b>
On Thu 12-12-19 11:04:27, Davidlohr Bueso wrote:
> There have been deadlock reports[1, 2] where put_page is called
> from softirq context and this causes trouble with the hugetlb_lock,
> as well as potentially the subpool lock.
>
> For such an unlikely scenario, lets not add irq dancing overhead
> to the lock+unlock operations, which could incur in expensive
> instruction dependencies, particularly when considering hard-irq
> safety. For example PUSHF+POPF on x86.
>
> Instead, just use a workqueue and do the free_huge_page() in regular
> task context.
I am afraid that work_struct is too large to be stuffed into the struct
page array (because of the lockdep part).
I think that it would be just safer to make hugetlb_lock irq safe. Are
there any other locks that would require the same?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-12-16 13:37 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-11 19:46 [PATCH v2] hugetlbfs: Disable softIRQ when taking hugetlb_lock Waiman Long
2019-12-11 22:04 ` Mike Kravetz
2019-12-11 22:19 ` Waiman Long
2019-12-12 1:11 ` Mike Kravetz
2019-12-12 6:06 ` Davidlohr Bueso
2019-12-12 6:30 ` Davidlohr Bueso
2019-12-12 19:04 ` [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue Davidlohr Bueso
2019-12-12 19:22 ` Mike Kravetz
2019-12-12 19:36 ` Davidlohr Bueso
2019-12-12 20:52 ` Waiman Long
2019-12-12 21:04 ` Waiman Long
2019-12-16 13:26 ` Michal Hocko
2019-12-16 15:38 ` Waiman Long
2019-12-16 18:44 ` Waiman Long
2019-12-17 9:00 ` Michal Hocko
2019-12-17 18:05 ` Mike Kravetz
2019-12-18 12:18 ` hugetlbfs testing coverage (was: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue) Michal Hocko
2019-12-12 21:01 ` [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue Waiman Long
2019-12-16 13:37 ` Michal Hocko [this message]
2019-12-16 16:17 ` Waiman Long
2019-12-16 16:17 ` Davidlohr Bueso
2019-12-16 17:18 ` Matthew Wilcox
2019-12-16 19:08 ` Mike Kravetz
2019-12-16 19:13 ` Waiman Long
2019-12-12 21:32 ` [PATCH v2] hugetlbfs: Disable softIRQ when taking hugetlb_lock Andi Kleen
2019-12-12 22:42 ` Davidlohr Bueso
2019-12-11 23:05 ` Andi Kleen
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