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

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Date:   Thu, 12 Dec 2019 14:42:44 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        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

On Thu, 12 Dec 2019, Andi Kleen wrote:

>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

Yep. I was only thinking about the workerfn not blocking
and therefore we could wait safely, but flush_work has no
such guarantees.

Thanks,
Davidlohr