Re: Regression: memory corruption on Atmel SAMA5D31

From: Tudor.Ambarus
Date: Mon Mar 07 2022 - 05:12:01 EST

On 3/4/22 18:48, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> On 3/4/22 14:38, Peter Rosin wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> Hi!
>
> Hi, Peter!
>
>>
>> On 2022-03-04 12:12, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
>>> Hi, Peter!
>>>
>>> On 3/4/22 12:57, Peter Rosin wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>
>>>> On 2022-03-04 07:57, Peter Rosin wrote:
>>>>> On 2022-03-04 04:55, Saravana Kannan wrote:
>>>>>> On Thu, Mar 3, 2022 at 1:17 AM Peter Rosin <peda@xxxxxxxxxx> wrote:
>>>>>>>
>>>>>>> On 2022-03-03 04:02, Saravana Kannan wrote:
>>>>>>>> On Wed, Mar 2, 2022 at 4:29 PM Peter Rosin <peda@xxxxxxxxxx> wrote:
>>>>>>>>>
>>>>>>>>> Hi!
>>>>>>>>>
>>>>>>>>> I'm seeing a weird problem, and I'd like some help with further
>>>>>>>>> things to try in order to track down what's going on. I have
>>>>>>>>> bisected the issue to
>>>>>>>>>
>>>>>>>>> f9aa460672c9 ("driver core: Refactor fw_devlink feature")
>>>>>>>>
>>>>>>>> I skimmed through your email and I'll read it more closely tomorrow,
>>>>>>>> but it wasn't clear if you see this on Linus's tip of the tree too.
>>>>>>>> Asking because of:
>>>>>>>> https://lore.kernel.org/lkml/20210930085714.2057460-1-yangyingliang@xxxxxxxxxx/
>>>>>>>>
>>>>>>>> Also, a couple of other data points that _might_ help. Try kernel
>>>>>>>> command line option fw_devlink=permissive vs fw_devlink=on (I forget
>>>>>>>> if this was the default by 5.10) vs fw_devlink=off.
>>>>>>>>
>>>>>>>> I'm expecting "off" to fix the issue for you. But if permissive vs on
>>>>>>>> shows a difference driver issues would start becoming a real
>>>>>>>> possibility.
>>>>>>>>
>>>>>>>> -Saravana
>>>>>>>
>>>>>>> Thanks for the quick reply! I don't think I tested the very tip of
>>>>>>> Linus tree before, only latest rc or something like that, but now I
>>>>>>> have. I.e.
>>>>>>>
>>>>>>> 5859a2b19911 ("Merge branch 'ucount-rlimit-fixes-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")
>>>>>>>
>>>>>>> It would have been typical if an issue that existed for a couple of
>>>>>>> years had been fixed the last few weeks, but alas, no.
>>>>>>>
>>>>>>> On that kernel, and with whatever the default fw_devlink value is, the
>>>>>>
>>>>>> It's fw_devlink=on by default from at least 5.12-rc4 or so.
>>>>>>
>>>>>>> issue is there. It's a bit hard to tell if the incident probability
>>>>>>> is the same when trying fw_devlink arguments, but roughly so, and I
>>>>>>> do not have to wait for long to get a bad hash with the first
>>>>>>> reproducer
>>>>>>>
>>>>>>> while :; do cat testfile | sha256sum; done
>>>>>>>
>>>>>>> The output is typical:
>>>>>>> 78464c59faa203413aceb5f75de85bbf4cde64f21b2d0449a2d72cd2aadac2a3 -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> e03c5524ac6d16622b6c43f917aae730bc0793643f461253c4646b860c1a7215 -
>>>>>>> 1b8db6218f481cb8e4316c26118918359e764cc2c29393fd9ef4f2730274bb00 -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 7d60bf848911d3b919d26941be33c928c666e9e5666f392d905af2d62d400570 -
>>>>>>> 212e1fe02c24134857ffb098f1834a2d87c655e0e5b9e08d4929f49a070be97c -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 7e33e751eb99a0f63b4f7d64b0a24f3306ffaf7c4bc4b27b82e5886c8ea31bc3 -
>>>>>>> d7a1f08aa9d0374d46d828fc3582f5927e076ff229b38c28089007cd0599c645 -
>>>>>>> 4fc963b7c7b14df9d669500f7c062bf378ff2751f705bb91eecd20d2f896f6fe -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>> 9360d886046c12d983b8bc73dd22302c57b0aafe58215700604fa977b4715fbe -
>>>>>>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d -
>>>>>>>
>>>>>>> Setting fw_devlink=off makes no difference, AFAICT.
>>>>>>
>>>>>> By this, I'm assuming you set fw_devlink=off in the kernel command
>>>>>> line and you still saw the corruption.
>>>>>
>>>>> Yes. On a bad kernel it's the same with all of the following kernel
>>>>> command lines.
>>>>>
>>>>> console=ttyS0,115200 rw oops=panic panic=30 fw_devlink=on ip=none root=ubi0:rootfs ubi.mtd=6 rootfstype=ubifs noinitrd mtdparts=atmel_nand:256k(at91bootstrap),384k(barebox),256k@768k(bareboxenv),256k(bareboxenv2),128k@1536k(oftree),5M@2M(kernel),248M@8M(rootfs),-@256M(ovlfs)
>>>>>
>>>>> console=ttyS0,115200 rw oops=panic panic=30 fw_devlink=off ip=none root=ubi0:rootfs ubi.mtd=6 rootfstype=ubifs noinitrd mtdparts=atmel_nand:256k(at91bootstrap),384k(barebox),256k@768k(bareboxenv),256k(bareboxenv2),128k@1536k(oftree),5M@2M(kernel),248M@8M(rootfs),-@256M(ovlfs)
>>>>>
>>>>> console=ttyS0,115200 rw oops=panic panic=30 fw_devlink=permissive ip=none root=ubi0:rootfs ubi.mtd=6 rootfstype=ubifs noinitrd mtdparts=atmel_nand:256k(at91bootstrap),384k(barebox),256k@768k(bareboxenv),256k(bareboxenv2),128k@1536k(oftree),5M@2M(kernel),248M@8M(rootfs),-@256M(ovlfs)
>>>>>
>>>>>> If that's the case, I can't see how this could possibly have anything
>>>>>> to do with:
>>>>>> f9aa460672c9 ("driver core: Refactor fw_devlink feature")
>>>>>>
>>>>>> If you look at fw_devlink_link_device(), you'll see that the function
>>>>>> is NOP if fw_devlink=off (the !fw_devlink_flags check). And from
>>>>>> there, the rest of the code in the series doesn't run because more
>>>>>> fields wouldn't get set, etc. That pretty much disables ALL the code
>>>>>> in the entire series. The only remaining diff would be header file
>>>>>> changes where I add/remove fields. But that's unlikely to cause any
>>>>>> issues here because I'm either deleting fields that aren't used or
>>>>>> adding fields that won't be used (with fw_devlink=off). I think the
>>>>>> patch was just causing enough timing changes that it's masking the
>>>>>> real issue.
>>>>>
>>>>> When I compare fw_devlink_link_device() from before and after
>>>>> f9aa460672c9 ("driver core: Refactor fw_devlink feature")
>>>>> I notice that you also removed an unconditional call to
>>>>> device_link_add_missing_supplier_links() that was live before,
>>>>> regardless of any fw_devlink parameter.
>>>>>
>>>>> I don't know if that's relevant. Is it?
>>>>>
>>>>> Not knowing this code at all, and without any serious attempt
>>>>> at reading it, from here the comment of that removed function
>>>>> sure looks like it might cause a different ordering before and
>>>>> after the patch that is not restored with any fw_devlink
>>>>> argument.
>>>>
>>>> It appears that the device_link_add_missing_supplier_links() difference
>>>> is not relevant after all. What actually happened in the header file in
>>>> the "bad" commit was that two fields were removed (none added). Like so:
>>>>
>>>> struct dev_links_info {
>>>> struct list_head suppliers;
>>>> struct list_head consumers;
>>>> - struct list_head needs_suppliers;
>>>> struct list_head defer_sync;
>>>> - bool need_for_probe;
>>>> enum dl_dev_state status;
>>>> };
>>>>
>>>> If I restore those fields on a bad kernel, the issue is no longer
>>>> visible. That is true for the first bad kernel, i.e.
>>>>
>>>> f9aa460672c9 ("driver core: Refactor fw_devlink feature")
>>>>
>>>> and for tip of Linus as of recently, i.e.
>>>>
>>>> 5859a2b19911 ("Merge branch 'ucount-rlimit-fixes-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")
>>>>
>>>> Which is of course insane and a whole different level of bad. WTF!?!
>>>>
>>>> I wonder if I can dig out the old SAMA5D31 evaluation kit and reproduce
>>>> there? I think that's next on the list...
>>>>
>>>
>>> I have a sama5d3_xplained that uses a SAMA5D36 and has a 256MBytes DDR2 and a
>>> 256MBytes NAND Flash. I tried a test with a 200MB file, rootfs on sdcard and
>>> I couldn't reproduce the bug. I'm using Linus's latest kernel:
>>> 38f80f42147f (HEAD, origin/master, origin/HEAD) MAINTAINERS: Remove dead patchwork link
>>>
>>> root@sama5d3-xplained-sd:~# dd if=/dev/urandom of=testfile bs=1024 count=200000
>>> 200000+0 records in
>>> 200000+0 records out
>>> 204800000 bytes (205 MB, 195 MiB) copied, 37.6424 s, 5.4 MB/s
>>> root@sama5d3-xplained-sd:~# for i in 1 2 3 4 5 6 7 8; do cat testfile | sha256sum; done
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> 2a4f1534aec6ace9d68f2f42fa28c1f1fe7bd281f960f2218797557aa41fe8de -
>>> root@sama5d3-xplained-sd:~#
>>>
>>> I'll put the rootfs on NAND and try to retest. Maybe to do some other tests
>>> in parallel to have more interrupts on the system. Will let you know if I can
>>> reproduce the bug on sama5d3_xplained.
>>
>> Thanks for testing!
>
> you're welcome, no worries.
>>
>> Since you (probably) don't have the interrupt source from the USB
>> serial chip that I have, that is not completely unexpected.
>>
>> $ lsusb
>> Bus 001 Device 002: ID 0403:6011 Future Technology Devices International, Ltd FT4232H Quad HS USB-UART/FIFO IC
>> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>> Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
>> $ cat /sys/bus/usb-serial/devices/ttyUSB?/latency_timer
>> 1
>> 1
>> 1
>> 1
>>
>> Also, your file is perhaps too small? You leave approx 50MB for the
>> system, so it might be the case that the page cache can hold the whole
>> file?
>>
>> So, can you please try that again with a slightly bigger file or if you
>> restrict how much RAM you allow the kernel to see?
>>
>> And if you don't have the FTDI usb-serial chip, you should probably go
>> with the other reproducer, namely to simply copy the random file to a
>> different host using scp.
>
> I kept the rootfs on sdcard but this time I generated a 300MB random file.
> I ran a mtd_stresstest on the NAND flash while doing the sha256sum or scp
> tests. All went fine.
>
> Here's the mtd_stresstest being successful https://pastebin.com/eWQNHAsE
> While the stresstest was running I did the following sha256 and scp tests:
> https://pastebin.com/wjutw63C
>
> On my laptop the sha256sum is matching the one on the board:
> $ sha256sum /tmp/testfile?
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile1
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile2
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile3
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile4
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile5
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile6
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile7
> d9232cee3ac29c3a9aaff8b23b4cb2914edd54e21550a555656988596fbd0b58 /tmp/testfile8
>
> Here's what "top" cmd was showing when doing the scp and the mtd_stresstest:
> top - 14:40:13 up 39 min, 3 users, load average: 1.95, 1.88, 1.80
> Tasks: 54 total, 3 running, 51 sleeping, 0 stopped, 0 zombie
> %Cpu(s): 35.1 us, 48.1 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 16.9 si, 0.0 st
> MiB Mem : 242.3 total, 2.5 free, 15.2 used, 224.6 buff/cache
> MiB Swap: 0.0 total, 0.0 free, 0.0 used. 220.1 avail Mem
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 464 root 20 0 4296 3292 2940 R 46.6 1.3 0:17.53 ssh
> 401 root 20 0 1668 760 676 R 45.0 0.3 17:57.11 modprobe
> 463 root 20 0 3456 2232 2000 S 5.2 0.9 0:02.04 scp
>
> Here's what "top" cmd was showing when doing the sha256sum and the mtd_stresstest:
> top - 14:12:47 up 12 min, 3 users, load average: 2.14, 1.92, 1.08
> Tasks: 54 total, 3 running, 51 sleeping, 0 stopped, 0 zombie
> %Cpu(s): 37.4 us, 58.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 4.2 si, 0.0 st
> MiB Mem : 242.3 total, 3.0 free, 14.8 used, 224.5 buff/cache
> MiB Swap: 0.0 total, 0.0 free, 0.0 used. 220.6 avail Mem
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 420 root 20 0 1396 784 692 R 47.2 0.3 0:06.42 sha256sum
> 401 root 20 0 1668 1208 1124 R 43.0 0.5 4:50.34 modprobe
> 419 root 20 0 1520 868 680 S 6.5 0.3 0:00.92 cat
>
> Peter, do you think it is worth to do some other tests on sama5d3_xplained?
> I'll try to find a SAMA5D31 evaluation kit meanwhile.
>

Peter, would it worth to do on your board a similar test to what I did?
I'm thinking whether the source of interrupts matters or not. So can you
disable your USB and use a mtd NAND stress test as a source of interrupts?
mtd_stresstest together with scp or hexdump.

Cheers,
ta