tst: Extend cross-test-ssh.sh to specify if target date can be altered

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.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/manual/install.texi b/manual/install.texi
index 419576f..eb41fbd 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -379,6 +379,26 @@ directory and @var{hostname} is the host name of a system that can run
 the newly built binaries of @theglibc{}.  The source and build
 directories must be visible at the same locations on both the build
 system and @var{hostname}.
+The @samp{cross-test-ssh.sh} script requires @samp{flock} from
+@samp{util-linux} to work when @var{glibc_test_allow_time_setting}
+environment variable is set.
+
+It is also possible to execute tests, which require setting the date on
+the target machine.  Following use cases are supported:
+@itemize @bullet
+@item
+@code{GLIBC_TEST_ALLOW_TIME_SETTING} is set in the environment in
+which eligible tests are executed and have the privilege to run
+@code{clock_settime}.  In this case, nothing prevents those tests from
+running in parallel, so the caller shall assure that those tests
+are serialized or provide a proper wrapper script for them.
+
+@item
+The @code{cross-test-ssh.sh} script is used and one passes the
+@option{--allow-time-setting} flag.  In this case, both sets
+@code{GLIBC_TEST_ALLOW_TIME_SETTING} and serialization of test
+execution are assured automatically.
+@end itemize
 
 In general, when testing @theglibc{}, @samp{test-wrapper} may be set
 to the name and arguments of any program to run newly built binaries.