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Thu, 13 Feb 2020 21:20:17 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 13 Feb 2020 13:19:47 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 13 Feb 2020 13:20:16 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 13 Feb 2020 13:20:16 -0800 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 13 Feb 2020 21:20:16 +0000 Subject: Re: [PATCH -next v2] mm: annotate a data race in page_zonenum() To: Qian Cai , CC: , , , , , , , References: <1581619089-14472-1-git-send-email-cai@lca.pw> From: John Hubbard X-Nvconfidentiality: public Message-ID: Date: Thu, 13 Feb 2020 13:20:15 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <1581619089-14472-1-git-send-email-cai@lca.pw> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1581628787; bh=HGGswWKrncPRu93Zq0PyM9U46WDVJ12jUnjbh/MB+io=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=GuiQ4sZ7GN6uyStZwg8bulXkQ+p9vDBfhMfkLVSOQ1eB7OYDPPbgMOBMWE6OfHD9z VylC9wTfTi82BTV8wqrfA+EEH+LGjCnZ9EwIwIY0qOTfluBB9529SzUgsyZXI0tRxl eWH/dxWUxgc9AC2oTHW+6na2CCTbxgUdhKXQyo61NytOjKrIJRWt3qFHgQ15+u7YeM /hDwdfToc9qj82HnGlukqlL3yLEuxkDbf1rV3ms5PqaNHhwiTRe0unZV2Dazu+iLnC fjWQSHyoKHSI3/F/+JnlXq3ozaxbofZhNnUpIZf1oePhfd9T+8cKvvXUNl7vz6Zjca cTTo3payr8upQ== 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 2/13/20 10:38 AM, Qian Cai wrote: > BUG: KCSAN: data-race in page_cpupid_xchg_last / put_page > > write (marked) to 0xfffffc0d48ec1a00 of 8 bytes by task 91442 on cpu 3: > page_cpupid_xchg_last+0x51/0x80 > page_cpupid_xchg_last at mm/mmzone.c:109 (discriminator 11) > wp_page_reuse+0x3e/0xc0 > wp_page_reuse at mm/memory.c:2453 > do_wp_page+0x472/0x7b0 > do_wp_page at mm/memory.c:2798 > __handle_mm_fault+0xcb0/0xd00 > handle_pte_fault at mm/memory.c:4049 > (inlined by) __handle_mm_fault at mm/memory.c:4163 > handle_mm_fault+0xfc/0x2f0 > handle_mm_fault at mm/memory.c:4200 > do_page_fault+0x263/0x6f9 > do_user_addr_fault at arch/x86/mm/fault.c:1465 > (inlined by) do_page_fault at arch/x86/mm/fault.c:1539 > page_fault+0x34/0x40 > > read to 0xfffffc0d48ec1a00 of 8 bytes by task 94817 on cpu 69: > put_page+0x15a/0x1f0 > page_zonenum at include/linux/mm.h:923 > (inlined by) is_zone_device_page at include/linux/mm.h:929 > (inlined by) page_is_devmap_managed at include/linux/mm.h:948 > (inlined by) put_page at include/linux/mm.h:1023 > wp_page_copy+0x571/0x930 > wp_page_copy at mm/memory.c:2615 > do_wp_page+0x107/0x7b0 > __handle_mm_fault+0xcb0/0xd00 > handle_mm_fault+0xfc/0x2f0 > do_page_fault+0x263/0x6f9 > page_fault+0x34/0x40 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 69 PID: 94817 Comm: systemd-udevd Tainted: G W O L 5.5.0-next-20200204+ #6 > Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 > > A page never changes its zone number. The zone number happens to be > stored in the same word as other bits which are modified, but the zone > number bits will never be modified by any other write, so it can accept > a reload of the zone bits after an intervening write and it don't need > to use READ_ONCE(). Thus, annotate this data race using > ASSERT_EXCLUSIVE_BITS() to also assert that there are no concurrent > writes to it. > > Suggested-by: Marco Elver > Signed-off-by: Qian Cai > --- > > v2: use ASSERT_EXCLUSIVE_BITS(). Much cleaner, thanks to this new macro. You can add: Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > > BTW, not sure if it is easier for Andrew with Paul to pick this up (with > Andrew's ACK), since ASSERT_EXCLUSIVE_BITS() is in -rcu tree only (or likely > tomorrow's -next tree). > > include/linux/mm.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 52269e56c514..0d70fafd055c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -920,6 +920,7 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, > > static inline enum zone_type page_zonenum(const struct page *page) > { > + ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT); > return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK; > } > >