From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Wed, 30 Mar 2016 23:40:00 +0200 (CEST) Received: from hauke-m.de ([5.39.93.123]:49156 "EHLO hauke-m.de" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S27014168AbcC3Vj47gCkw (ORCPT ); Wed, 30 Mar 2016 23:39:56 +0200 Received: from [192.168.178.24] (pD9F60AA0.dip0.t-ipconnect.de [217.246.10.160]) by hauke-m.de (Postfix) with ESMTPSA id 0C0A110029B; Wed, 30 Mar 2016 23:39:56 +0200 (CEST) Subject: Re: [PATCH v2] MIPS: vdso: flush the vdso data page to update it on all processes To: Zubair Lutfullah Kakakhel , linux-mips@linux-mips.org, ralf@linux-mips.org References: <1456074518-13163-1-git-send-email-hauke@hauke-m.de> <56FAF575.4070607@hauke-m.de> <56FBEEFF.10406@imgtec.com> Cc: alex.smith@imgtec.com, sergei.shtylyov@cogentembedded.com, "# v4 . 4+" From: Hauke Mehrtens Message-ID: <56FC472B.1040801@hauke-m.de> Date: Wed, 30 Mar 2016 23:37:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.6.0 MIME-Version: 1.0 In-Reply-To: <56FBEEFF.10406@imgtec.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 52799 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: hauke@hauke-m.de Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On 03/30/2016 05:21 PM, Zubair Lutfullah Kakakhel wrote: > Hi Hauke, > > Could you share details of what version of glibc/rfs setup you are using? Hi, I am using the musl libc version 1.1.4 in OpenWrt. musl uses the same vdso code on arm and x86, it just needed some extensions to support the -ENOSYS return value which is not returned by the other architectures. I removed the following patches from OpenWrt to activate vdso gettimeofday in kernel 4.4 again: target/linux/generic/patches-4.4/206-mips-disable-vdso.patch target/linux/generic/patches-4.4/340-MIPS-deactivate-gettimeofday-vdso.patch > > Thanks. > > Regards, > ZubairLK > > On 29/03/16 22:36, Hauke Mehrtens wrote: >> On 02/21/2016 06:08 PM, Hauke Mehrtens wrote: >>> Without flushing the vdso data page the vdso call is working on dated >>> or unsynced data. This resulted in problems where the clock_gettime >>> vdso call returned a time 6 seconds later after a 3 seconds sleep, >>> while the syscall reported a time 3 sounds later, like expected. This >>> happened very often and I got these ping results for example: >>> >>> root@OpenWrt:/# ping 192.168.1.255 >>> PING 192.168.1.255 (192.168.1.255): 56 data bytes >>> 64 bytes from 192.168.1.3: seq=0 ttl=64 time=0.688 ms >>> 64 bytes from 192.168.1.3: seq=1 ttl=64 time=4294172.045 ms >>> 64 bytes from 192.168.1.3: seq=2 ttl=64 time=4293968.105 ms >>> 64 bytes from 192.168.1.3: seq=3 ttl=64 time=4294055.920 ms >>> 64 bytes from 192.168.1.3: seq=4 ttl=64 time=4294671.913 ms >>> >>> This was tested on a Lantiq/Intel VRX288 (MIPS BE 34Kc V5.6 CPU with >>> two VPEs) >>> >>> Signed-off-by: Hauke Mehrtens >>> Cc: # v4.4+ >> >> This patch flushes the complete dcache of the CPU if cpu_has_dc_aliases >> is set. >> >> Calling flush_dcache_page(virt_to_page(&vdso_data)); improved the >> situation a litte bit but did not fix my problem. >> >> Could someone from Imagination please look into this problem. The page >> is linked into many virtual address spaces and when it gets modified by >> the kernel the user space processes are still accessing partly old data, >> even when lush_dcache_page() was called. >> >>> --- >>> arch/mips/kernel/vdso.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c >>> index 975e997..8b0d974 100644 >>> --- a/arch/mips/kernel/vdso.c >>> +++ b/arch/mips/kernel/vdso.c >>> @@ -20,6 +20,8 @@ >>> #include >>> >>> #include >>> +#include >>> +#include >>> #include >>> >>> /* Kernel-provided data used by the VDSO. */ >>> @@ -85,6 +87,8 @@ void update_vsyscall(struct timekeeper *tk) >>> } >>> >>> vdso_data_write_end(&vdso_data); >>> + flush_cache_vmap((unsigned long)&vdso_data, >>> + (unsigned long)&vdso_data + sizeof(vdso_data)); >>> } >>> >>> void update_vsyscall_tz(void) >>> @@ -93,6 +97,8 @@ void update_vsyscall_tz(void) >>> vdso_data.tz_minuteswest = sys_tz.tz_minuteswest; >>> vdso_data.tz_dsttime = sys_tz.tz_dsttime; >>> } >>> + flush_cache_vmap((unsigned long)&vdso_data, >>> + (unsigned long)&vdso_data + sizeof(vdso_data)); >>> } >>> >>> int arch_setup_additional_pages(struct linux_binprm *bprm, int >>> uses_interp) >>> >> >>