[LTP] [PATCH] fzsync: skip test when avaliable CPUs less than 2

Joerg Vehlow
2020-11-30T07:53:46Z

Hi,
>> No, af_alg07 requires 2 CPUs, otherwise it'll report false positives.
>> The test will pass only if fchownat() hits a half-closed socket and
>> returns error. But IIRC the half-closed socket will be destroyed during
>> reschedule which means there's no race window to hit anymore. But it
>> would be better to put the TCONF condition into the test itself.
> Interesting, I wonder if this is also true for the real-time kernel with
> the threads set to RT priority?
It looks like the test can fail even with more than one cpu. I've seen
this sporadic failure on different hardware with more than two cores, at
least on intel denverton (x86_64) and renesas r-car (aarch64) systems.
Both with kernel 4.19 with the fix included, on the denverton system the
rt parches were included and on the r-car not. The test passes most of
the time, but sometimes fails with the message Li posted.

It also seems to fail sporadically on other systems as well:
https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/1892860

Additionally I tested on qemu-x86 with 4.19 with and without rt patches.
The test succeeds even with only one virtualized cpu. So either Martin's
assumption is wrong or it holds only for newer kernel versions?

J?rg