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[47.88.44.36]) by mx.google.com with ESMTPS id t20si23812125pfh.238.2019.05.21.18.01.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 May 2019 18:01:03 -0700 (PDT) Received-SPF: pass (google.com: domain of yang.shi@linux.alibaba.com designates 47.88.44.36 as permitted sender) client-ip=47.88.44.36; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yang.shi@linux.alibaba.com designates 47.88.44.36 as permitted sender) smtp.mailfrom=yang.shi@linux.alibaba.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R611e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04446;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0TSLG0uI_1558486838; Received: from 192.168.1.105(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TSLG0uI_1558486838) by smtp.aliyun-inc.com(127.0.0.1); Wed, 22 May 2019 09:00:47 +0800 Subject: Re: [v3 PATCH] mm: mmu_gather: remove __tlb_reset_range() for force flush To: Andrew Morton Cc: jstancek@redhat.com, peterz@infradead.org, will.deacon@arm.com, npiggin@gmail.com, aneesh.kumar@linux.ibm.com, namit@vmware.com, minchan@kernel.org, mgorman@suse.de, stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1558322252-113575-1-git-send-email-yang.shi@linux.alibaba.com> <20190521161826.029782de0750c8f5cd2e5dd6@linux-foundation.org> From: Yang Shi Message-ID: <9c27f777-3330-8e43-e4cf-cc4d9c3e0229@linux.alibaba.com> Date: Wed, 22 May 2019 09:00:34 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190521161826.029782de0750c8f5cd2e5dd6@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US 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 5/22/19 7:18 AM, Andrew Morton wrote: > On Mon, 20 May 2019 11:17:32 +0800 Yang Shi wrote: > >> A few new fields were added to mmu_gather to make TLB flush smarter for >> huge page by telling what level of page table is changed. >> >> __tlb_reset_range() is used to reset all these page table state to >> unchanged, which is called by TLB flush for parallel mapping changes for >> the same range under non-exclusive lock (i.e. read mmap_sem). Before >> commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in >> munmap"), the syscalls (e.g. MADV_DONTNEED, MADV_FREE) which may update >> PTEs in parallel don't remove page tables. But, the forementioned >> commit may do munmap() under read mmap_sem and free page tables. This >> may result in program hang on aarch64 reported by Jan Stancek. The >> problem could be reproduced by his test program with slightly modified >> below. >> >> ... >> >> Use fullmm flush since it yields much better performance on aarch64 and >> non-fullmm doesn't yields significant difference on x86. >> >> The original proposed fix came from Jan Stancek who mainly debugged this >> issue, I just wrapped up everything together. > Thanks. I'll add > > Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") > > to this. Thanks, Andrew.