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Thu, 12 Dec 2019 20:52:21 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-59.bos.redhat.com [10.18.17.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id A4AC65D9CA; Thu, 12 Dec 2019 20:52:20 +0000 (UTC) Subject: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue To: Mike Kravetz , Andrew Morton , Matthew Wilcox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , aneesh.kumar@linux.ibm.com References: <20191211194615.18502-1-longman@redhat.com> <4fbc39a9-2c9c-4c2c-2b13-a548afe6083c@oracle.com> <32d2d4f2-83b9-2e40-05e2-71cd07e01b80@redhat.com> <0fcce71f-bc20-0ea3-b075-46592c8d533d@oracle.com> <20191212060650.ftqq27ftutxpc5hq@linux-p48b> <20191212063050.ufrpij6s6jkv7g7j@linux-p48b> <20191212190427.ouyohviijf5inhur@linux-p48b> From: Waiman Long Organization: Red Hat Message-ID: <79d3a7e1-384b-b759-cd84-56253fb9ed40@redhat.com> Date: Thu, 12 Dec 2019 15:52:20 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/12/19 2:22 PM, Mike Kravetz wrote: > On 12/12/19 11:04 AM, 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. >> >> [1] https://lore.kernel.org/lkml/20191211194615.18502-1-longman@redhat.com/ >> [2] https://lore.kernel.org/lkml/20180905112341.21355-1-aneesh.kumar@linux.ibm.com/ >> >> Reported-by: Waiman Long >> Reported-by: Aneesh Kumar K.V >> Signed-off-by: Davidlohr Bueso > Thank you Davidlohr. > > The patch does seem fairly simple and straight forward. I need to brush up > on my workqueue knowledge to provide a full review. > > Longman, > Do you have a test to reproduce the issue? If so, can you try running with > this patch. Yes, I do have a test that can reproduce the issue. I will run it with the patch and report the status tomorrow. -Longman