[v6] 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.

Changes for v2:
- Utilize flock to provide serialization of cross-test-ssh.sh script
  execution.
- Add entry to manual/install.texi about --allow-time-setting flag
  usage.

Changes for v3:
- The install.texi manual has been augmented to explain two distinct
  use cases for setting the time on target system.

Changes for v4:
- Add -w switch to flock (specify timeout)
- Check return value of flock - exit ssh shell script
- Allow user override of FLOCK_* variables
- Rewrite the script's information/help text
- Rewrite the install.texi manual entry for this
  script usage

Changes for v5:
- Add two spaces after '.'
- Add information to INSTALL file that 'flock' from util-linux is
  required to provide serialization
- Add information to INSTALL about flock need for test wrapper

Changes for v6:
- Move the information about 'flock' requirement from INSTALL to
  install.texi
---
 manual/install.texi       | 20 ++++++++++++++++++++
 scripts/cross-test-ssh.sh | 25 ++++++++++++++++++++++++-
 2 files changed, 44 insertions(+), 1 deletion(-)

On 03/03/2021 18:46, 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.
> 
> Changes for v2:
> - Utilize flock to provide serialization of cross-test-ssh.sh script
>   execution.
> - Add entry to manual/install.texi about --allow-time-setting flag
>   usage.
> 
> Changes for v3:
> - The install.texi manual has been augmented to explain two distinct
>   use cases for setting the time on target system.
> 
> Changes for v4:
> - Add -w switch to flock (specify timeout)
> - Check return value of flock - exit ssh shell script
> - Allow user override of FLOCK_* variables
> - Rewrite the script's information/help text
> - Rewrite the install.texi manual entry for this
>   script usage
> 
> Changes for v5:
> - Add two spaces after '.'
> - Add information to INSTALL file that 'flock' from util-linux is
>   required to provide serialization
> - Add information to INSTALL about flock need for test wrapper
> 
> Changes for v6:
> - Move the information about 'flock' requirement from INSTALL to
>   install.texi

As Joseph has noted, you need to regenerate the INSTALL and send it 
along with the patch itself (as other patches to INSTALL).  The
glibc regeneration wiki shows how to do it [1]

  INSTALL is generated by makeinfo; run rm $srcdir/INSTALL; make INSTALL 
  to regenerate it (from the object directory). Currently we use texinfo 
  version 6.5.

Please send a v7 with the INSTALL change as well.

[1] https://sourceware.org/glibc/wiki/Regeneration

> ---
>  manual/install.texi       | 20 ++++++++++++++++++++
>  scripts/cross-test-ssh.sh | 25 ++++++++++++++++++++++++-
>  2 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/manual/install.texi b/manual/install.texi
> index 419576f49c..828c78ee1f 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 requres @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 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 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 it.
> +
> +@item
> +The @code{cross-test-ssh.sh} script is used and one passes the
> +@option{--allow-time-setting} flag.  In this case both setting
> +@code{GLIBC_TEST_ALLOW_TIME_SETTING} and serialization of tests
> +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.
> diff --git a/scripts/cross-test-ssh.sh b/scripts/cross-test-ssh.sh
> index 6d8fbcdfd2..a839e22dd0 100755
> --- a/scripts/cross-test-ssh.sh
> +++ b/scripts/cross-test-ssh.sh
> @@ -22,7 +22,7 @@
>  
>  progname="$(basename $0)"
>  
> -usage="usage: ${progname} [--ssh SSH] HOST COMMAND ..."
> +usage="usage: ${progname} [--ssh SSH] [--allow-time-setting] HOST COMMAND ..."
>  help="Run a glibc test COMMAND on the remote machine HOST, via ssh,
>  preserving the current working directory, and respecting quoting.
>  
> @@ -32,6 +32,10 @@ instead of ordinary 'ssh'.
>  If the '--timeoutfactor FACTOR' flag is present, set TIMEOUTFACTOR on
>  the remote machine to the specified FACTOR.
>  
> +If the '--allow-time-setting' flag is present, set
> +GLIBC_TEST_ALLOW_TIME_SETTING on the remote machine to indicate that
> +time can be safely adjusted (e.g. on a virtual machine).
> +
>  To use this to run glibc tests, invoke the tests as follows:
>  
>    $ make test-wrapper='ABSPATH/cross-test-ssh.sh HOST' tests
> @@ -81,6 +85,10 @@ while [ $# -gt 0 ]; do
>        timeoutfactor="$1"
>        ;;
>  
> +    "--allow-time-setting")
> +      settimeallowed="1"
> +      ;;
> +
>      "--help")
>        echo "$usage"
>        echo "$help"
> @@ -127,6 +135,21 @@ if [ "$timeoutfactor" ]; then
>  ${command}"
>  fi
>  
> +# Add command to set the info that time on target can be adjusted,
> +# if required.
> +# Serialize execution of this script on target to prevent from unintended
> +# change of target time.
> +FLOCK_PATH="${FLOCK_PATH:-/var/lock/clock_settime}"
> +FLOCK_TIMEOUT="${FLOCK_TIMEOUT:-20}"
> +FLOCK_FD="${FLOCK_FD:-99}"
> +if [ "$settimeallowed" ]; then
> +  command="exec ${FLOCK_FD}<>${FLOCK_PATH}
> +flock -w ${FLOCK_TIMEOUT} ${FLOCK_FD}
> +if [ $? -ne 0 ]; then exit 1; fi
> +export GLIBC_TEST_ALLOW_TIME_SETTING=1
> +${command}"
> +fi
> +
>  # HOST's sshd simply concatenates its arguments with spaces and
>  # passes them to some shell.  We want to force the use of /bin/sh,
>  # so we need to re-quote the whole command to ensure it appears as
>