From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailapp01.imgtec.com ([195.59.15.196]:21119 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752953AbcC3PWM (ORCPT ); Wed, 30 Mar 2016 11:22:12 -0400 Subject: Re: [PATCH v2] MIPS: vdso: flush the vdso data page to update it on all processes To: Hauke Mehrtens , , References: <1456074518-13163-1-git-send-email-hauke@hauke-m.de> <56FAF575.4070607@hauke-m.de> CC: , , "# v4 . 4+" From: Zubair Lutfullah Kakakhel Message-ID: <56FBEEFF.10406@imgtec.com> Date: Wed, 30 Mar 2016 16:21:35 +0100 MIME-Version: 1.0 In-Reply-To: <56FAF575.4070607@hauke-m.de> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: Hi Hauke, Could you share details of what version of glibc/rfs setup you are using? 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) >> > >