From: Waiman Long <firstname.lastname@example.org>
To: Michal Hocko <email@example.com>, Davidlohr Bueso <firstname.lastname@example.org>
Cc: Andrew Morton <email@example.com>,
Mike Kravetz <firstname.lastname@example.org>,
Matthew Wilcox <email@example.com>,
Subject: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue
Date: Mon, 16 Dec 2019 11:17:00 -0500 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 12/16/19 8:37 AM, Michal Hocko wrote:
> 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?
Currently, free_huge_page() can be called from the softIRQ context. The
hugetlb_lock will be acquired during that call. The subpool lock may
conditionally be acquired as well.
I am still torn between converting both locks to be irq-safe or
deferring the freeing to a workqueue.
next prev parent reply other threads:[~2019-12-16 16:17 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
2019-12-16 16:17 ` Waiman Long [this message]
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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