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>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org 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: <email@example.com> (raw) In-Reply-To: <20191216133711.GH30281@dhcp22.suse.cz> 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. Cheers, Longman
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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