linux-kernel - Re: [PATCH v2] hugetlbfs: Disable softIRQ when taking hugetlb

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Date:   Thu, 12 Dec 2019 13:32:39 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     Waiman Long <longman@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH v2] hugetlbfs: Disable softIRQ when taking hugetlb_lock

Davidlohr Bueso <dave@...olabs.net> writes:
> +void free_huge_page(struct page *page)
> +{
> +	struct hugetlb_free_page_work work;
> +
> +	work.page = page;
> +	INIT_WORK_ONSTACK(&work.work, free_huge_page_workfn);
> +	queue_work(hugetlb_free_page_wq, &work.work);
> +
> +	/*
> +	 * Wait until free_huge_page is done.
> +	 */
> +	flush_work(&work.work);
> +	destroy_work_on_stack(&work.work);

Does flushing really work in softirq context?

Anyways, waiting seems inefficient over fire'n'forget

You'll need a per cpu pre allocated work item and a queue.
Then take a lock on the the queue and link the page into
it and trigger the work item if it's not already pending.

And add a in_interrupt() check of course.


-Andi