Re: [PATCH v2 1/3] tst: Extend cross-test-ssh.sh to specify if target date can be altered

[Joseph Myers <joseph@codesourcery.com>]

On Sat, 6 Feb 2021, Lukasz Majewski wrote:

> This code adds new flag - '--allow-time-setting' to cross-test-ssh.sh
> script to indicate if it is allowed to alter the date on the system
> on which tests are executed. This change is supposed to be used with
> test systems, which use virtual machines for testing.
> 
> The GLIBC_TEST_ALLOW_TIME_SETTING env variable is exported to the
> remote environment on which the eligible test is run and brings no
> functional change when it is not.

I think there are two separate features here, both of which should be 
documented.  The ability to run tests that set the time should not be 
limited to when cross-test-ssh.sh is used; someone might want to write 
their own test wrapper supporting that feature (there's no requirement to 
use the provided test wrapper, writing your own is fully supported), or 
might want to run tests with setting time enabled for native testing (for 
example, if they have a build and test environment that creates a virtual 
machine to run "make check" natively on it and then destroys that virtual 
machine afterwards).

So at least two things should be documented:

* If you set GLIBC_TEST_ALLOW_TIME_SETTING in the environment in which 
tests are run *and* run the tests with appropriate privileges to be able 
to use clock_settime, then such tests will be run, but this will not by 
itself provide any locking against conflicting tests running in parallel 
so you should also either test in series or use a test wrapper that 
provides such locking.

* In the case of using cross-test-ssh.sh, you can pass the 
--allow-time-setting option to automate both setting 
GLIBC_TEST_ALLOW_TIME_SETTING and doing the locking.

-- 
Joseph S. Myers
joseph@codesourcery.com