[CRIU] [RFC v2 3/5] zdtm: add reset_pid() function

[Andrei Vagin]

On Thu, Mar 23, 2017 at 07:59:16PM +0000, Adrian Reber wrote:
> From: Adrian Reber <areber at redhat.com>
> 
> In preparation for the zdtm option '--check-only' a new helper function
> reset_pid() is added which writes to ns_last_pid to avoid PID collisions
> during check-only restore and the real restore.
> 
> Signed-off-by: Adrian Reber <areber at redhat.com>
> ---
>  test/zdtm.py | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/test/zdtm.py b/test/zdtm.py
> index 57e2ab0..8d38e05 100755
> --- a/test/zdtm.py
> +++ b/test/zdtm.py
> @@ -329,6 +329,13 @@ def wait_pid_die(pid, who, tmo = 30):
>  def test_flag(tdesc, flag):
>  	return flag in tdesc.get('flags', '').split()
>  
> +
> +def reset_pid(pid = 1):

I don't understand how pid = 1 helps to avoid collisions. We create a
new pid namespace for each test (test/zdtm_ct) and we know that pids are
allocated sequentialy, so test process uses
"small" pids. In this case setting 1 into ns_last_pid has to increate
probability of collisions...


> +	fd = open('/proc/sys/kernel/ns_last_pid', 'w')
> +	fd.write('%s' % pid)
> +	fd.close()
> +
> +
>  #
>  # Exception thrown when something inside the test goes wrong,
>  # e.g. test doesn't start, criu returns with non zero code or
> -- 
> 1.8.3.1
> 
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