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, 15 insertions, 0 deletions

diff --git a/INSTALL b/INSTALL
index 9a50e3ee06..065a568585 100644
--- a/INSTALL
+++ b/INSTALL
@@ -347,6 +347,21 @@ is the absolute directory name for the main source directory and
 HOSTNAME is the host name of a system that can run the newly built
 binaries of the GNU C Library.  The source and build directories must be
 visible at the same locations on both the build system and HOSTNAME.
+The 'cross-test-ssh.sh' script requires 'flock' from 'util-linux' to
+work when 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:
+   * 'GLIBC_TEST_ALLOW_TIME_SETTING' is set in the environment in which
+     eligible tests are executed and have the privilege to run
+     '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.
+
+   * The 'cross-test-ssh.sh' script is used and one passes the
+     '--allow-time-setting' flag.  In this case, both sets
+     'GLIBC_TEST_ALLOW_TIME_SETTING' and serialization of test execution
+     are assured automatically.
 
    In general, when testing the GNU C Library, 'test-wrapper' may be set
 to the name and arguments of any program to run newly built binaries.