From 621fae3cbc79eb4d0277c40993328faa4019e95f Mon Sep 17 00:00:00 2001
From: Sergei Golubchik <serg@mariadb.org>
Date: Tue, 6 Jul 2021 11:36:59 +0200
Subject: [PATCH] MDEV-25802 mtr: race condition if the test quickly restarts
 twice

part II

need to tell SafeProcess not to collect the exited mysqld
in sleep_until_file_created(), so that it would be found in the
later wait_any_timeout() in run_testcase()

Removed a strange condition in SafeProcess::wait_one()
that treated return value of -1 from waitpid() as "process exists"
instead of as "no such child process" (see `perldoc -f waitpid`)
---
 mysql-test/lib/My/SafeProcess.pm | 18 +++++++++---------
 mysql-test/lib/mtr_process.pl    |  2 +-
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/mysql-test/lib/My/SafeProcess.pm b/mysql-test/lib/My/SafeProcess.pm
index 4f7464daf44..30c8fe54642 100644
--- a/mysql-test/lib/My/SafeProcess.pm
+++ b/mysql-test/lib/My/SafeProcess.pm
@@ -395,10 +395,10 @@ sub _collect {
 #  1 Still running
 #
 sub wait_one {
-  my ($self, $timeout)= @_;
-  croak "usage: \$safe_proc->wait_one([timeout])" unless ref $self;
+  my ($self, $timeout, $keep)= @_;
+  croak "usage: \$safe_proc->wait_one([timeout] [, keep])" unless ref $self;
 
-  _verbose("wait_one $self, $timeout");
+  _verbose("wait_one $self, $timeout, $keep");
 
   if ( ! defined($self->{SAFE_PID}) ) {
     # No pid => not running
@@ -472,16 +472,16 @@ sub wait_one {
     return 1;
   }
 
-  if ( not $blocking and $retpid == -1 ) {
-    # still running
-    _verbose("still running");
-    return 1;
-  }
+  #if ( not $blocking and $retpid == -1 ) {
+  #  # still running
+  #  _verbose("still running");
+  #  return 1;
+  #}
 
   #warn "wait_one: expected pid $pid but got $retpid"
   #  unless( $retpid == $pid );
 
-  $self->_collect($exit_code);
+  $self->_collect($exit_code) unless $keep;
   return 0;
 }
 
diff --git a/mysql-test/lib/mtr_process.pl b/mysql-test/lib/mtr_process.pl
index c568f8dc48c..2ff78c0e10a 100644
--- a/mysql-test/lib/mtr_process.pl
+++ b/mysql-test/lib/mtr_process.pl
@@ -121,7 +121,7 @@ sub sleep_until_file_created ($$$$$) {
     my $seconds= ($loop * $sleeptime) / 1000;
 
     # Check if it died after the fork() was successful
-    if ( defined $proc and ! $proc->wait_one(0) )
+    if ( defined $proc and ! $proc->wait_one(0, 1) )
     {
       return 1 if -r $expectfile;
       mtr_warning("Process $proc died after mysql-test-run waited $seconds " .