On 05/07/2018 01:16 PM, Daniel Danzberger wrote: > On 05/06/2018 09:00 PM, Rosen Penev wrote: >> On Sun, May 6, 2018 at 10:08 AM, Rosen Penev <ros...@gmail.com> wrote: >>> On Sun, May 6, 2018 at 3:52 AM, Daniel Danzberger <dan...@dd-wrt.com> wrote: >>>> MMAP'ed memory that has been allocated via 'get_zeroed_page(GFP_KERNEL)' or >>>> 'vmalloc()' doesn't always contain the same data when accessed from >>>> userspace. >>>> >>>> This means all userspace programs using mmap to access kernel memory aren't >>>> always working properly on the Rambutan board. I am currently testing if >>>> other >>>> ar71xx devices are affected as well. >>>> >>>> I first noticed this when using ALSA's mmap api to capture audio. >>>> >>>> Here is the feed for a kmod + userpace util to reproduce the issue: >>>> g...@github.com:dddaniel/mmaptest.git >>>> >>>> The kernel module simply allocates a page and initializes it with 0xff. >>>> The userspace application then mmap's and reads this page 10 times with a >>>> 500ms >>>> delay an checks if all data is 0xff. >>>> >>>> --- >>>> root@OpenWrt:/# mmaptest-user >>>> mmap addr: 0x77a04000 >>>> [ 760.464968] mmap page 7573000 at va 87573000 >>>> check memory ...FAIL (at byte 0) >>>> check memory ...FAIL (at byte 96) >>>> check memory ...FAIL (at byte 96) >>>> check memory ...FAIL (at byte 96) >>>> check memory ...FAIL (at byte 128) >>>> --- >>>> >>>> I have no idea whats causing it. Does anybody have a hint on how to fix >>>> this ? >>>> >>> Try reverting >>> https://github.com/torvalds/linux/commit/c00ab4896ed5f7d89af6f90b809e2c0197c6d170 >> Disregard that. That commit should have no impact. >> >> I just tested it on an Archer C7v4 and the issue is present as well. >> This was probably causing data corruption for me when I used an >> external hard drive... >> >> Strange that sometimes it works and sometimes not.Yes, the same in my tests. >> Look's like this issue appears on all ar71xx devices. >> >> Did you encounter this issue with kernel 4.9? For me, 4.4 caused no >> data corruption on my external hard drive. > I can't tell right now. I was trying to use an older version with kernel 4.4, > but it fails to build. I just tested with 4.4 and the problem is present there as well. >> >> There seems to be a pattern with kernel 4.9 breaking various MIPS devices... > >>>> -- >>>> Regards >>>> >>>> Daniel Danzberger >>>> embeDD GmbH, Alter Postplatz 2, CH-6370 Stans >>>> >>>> _______________________________________________ >>>> Lede-dev mailing list >>>> Lede-dev@lists.infradead.org >>>> http://lists.infradead.org/mailman/listinfo/lede-dev >> >
-- Regards Daniel Danzberger embeDD GmbH, Alter Postplatz 2, CH-6370 Stans _______________________________________________ Lede-dev mailing list Lede-dev@lists.infradead.org http://lists.infradead.org/mailman/listinfo/lede-dev
