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[Discuss] Linux on Lenovo P70 -- data corruption

On 09/04/2017 02:10 PM, Robert Krawitz wrote:
> On Mon, 4 Sep 2017 13:59:48 -0400, Frank DiPrete wrote:
>> What us the NIC in the laptop ?
>> I've had this problem before using the open source driver for a network
>> adapter.
>> (trying to remember which one)
> But this appears to also happen over the loopback interface.

If you can reliably get it to mess up, see what reliably never messes 
up, squeeze between the two.

Two hunches:

#1 This has nothing to do with networking, it is a local problem that 
kernel caching hides when doing local operations; with network 
operations the kernel can't make the same assumptions.

#2 This is a driver bug. What unique-ish hardware does this machine 
have? Can you run tests that exclude that hardware?

I would try more experiments along these lines:

  - Remove RAM, so the kernel can't do as much caching.

  - Turn off swap.

  - Create some files on a different (working) machine that have known 
contents: bigger-than-your-RAM patterned data, and bigger-than-your-RAM 
data files from urandom (SHA-256 is a way to check random data files)...

  - Transfer them into this machine in different ways: wired network, 
wireless, builtin interfaces, USB network interfaces, USB flash drive, 
USB spinning disk drive, USB 3.0, USB <3.0...

  - Transfer them to different places: RAM disk, each SSD, USB flash 
drive, USB spinning drive, loopback volume, different kinds of formatted 
filesystems on these, right back out the network without ever storing 
locally, into a RAM buffer of a trivial C program you write for the purpose.

  - Try an obsolete kernel, in a graphical UI, in a text console...

  - Try repeated SHA hashes of stored files (stored in different places) 
see whether they are consistent.

Keep careful notes, look for patterns, hope it becomes clear before you 
give up.

Report back!

-kb, the Kent whose old Lenovo liked to freeze up when doing lots of 
video blitting near the edge of the display, until a new version of 
Debian fixed it.

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