On 05-07-19 00:59, Willem de Bruijn wrote:
Can you reproduce the issue when running the modified test in a
network namespace (./in_netns.sh ./txring_overwrite)?
But even when running the test with ./in_netns.sh it shows
"wrong pattern", this time without length mismatches:
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
wrong pattern: 0x62 != 0x61
As already mentioned, it seems to trigger mainly (only ?) when
an USB device is connected. The PC I'm testing this on has an
USB hub with many ports and connected devices. When connecting
this USB hub, the amount of "wrong pattern" errors that are
shown seems to correlate to the amount of new devices
that the kernel should detect. Connecting in a single USB device
also triggers the error, but not on every attempt.
Unfortunately have not found any other way to force the
error to trigger. E.g. running stress-ng to generate CPU load or
timer interrupts does not seem to have any impact.
Interesting, thanks for testing. No exact idea so far. The USB devices
are not necessarily network devices, I suppose? I don't immediately
have a setup to test the usb hotplug, so cannot yet reproduce the bug.
It triggers with different types of USB devices. Verified the
bug can trigger with an USB flash drive, mouse, USB-serial
adapter and USB hub (also with no devices connected).
It can trigger when the USB device is connected as well as when
it's disconnected. But there is a bit of luck needed, it can take
a bunch of times before it happens. Using a large USB hub with
many connected devices will trigger it much easier.
