MDEV-34753 memory pressure - erroneous termination condition

The 'if (!m_abort) break' condition was inverted by accident.

Constrain the test case to environments where there is cgroupv2
runtime environment which is the same case that will pass a memory
pressure initialization.

Remove the explicit garbage_collection trigger as it hides the abnormal
termination error on the event loop for memory pressure. This
also means there is no support in non-cgroupv2 environments
(possibly some container environments).

As the trigger to memory pressure is via a different thread we
need to wait until a "[mM]emory pressure" log message is there to
know it has succeeded or failed.

Thanks Kristian Nielsen for noticing and review.

mysql-test/include/have_cgroupv2.inc

@@ -0,0 +1,28 @@
+--source include/linux.inc
+--error 0,1
+perl;
+use strict;
+use warnings;
+use File::Spec;
+
+# Read the cgroup file
+my $cgroup_file = '/proc/self/cgroup';
+open my $fh, '<', $cgroup_file or exit 1;
+my $line = <$fh>;
+close $fh;
+
+# Process the cgroup file content
+$line =~ s/^0:://;
+chomp($line);
+
+# Construct the path
+my $path = File::Spec->catdir('/sys/fs/cgroup', $line, 'memory.pressure');
+
+# Check if the file is writable exists
+exit 0 if -w $path;
+exit 1;
+EOF
+if ($errno)
+{
+  --skip Requires cgroupv2
+}

mysql-test/suite/innodb/r/mem_pressure.result

@@ -15,6 +15,7 @@ FROM INFORMATION_SCHEMA.GLOBAL_STATUS
 WHERE VARIABLE_NAME='Innodb_buffer_pool_pages_dirty';
 set debug_dbug="d,trigger_garbage_collection";
 SET GLOBAL innodb_buffer_pool_size=@@innodb_buffer_pool_size;
+FOUND 1 /[Mm]emory pressure.*/ in mysqld.1.err
 SELECT CAST(VARIABLE_VALUE AS INTEGER) < @dirty_prev AS LESS_DIRTY_IS_GOOD
 FROM INFORMATION_SCHEMA.GLOBAL_STATUS
 WHERE VARIABLE_NAME='Innodb_buffer_pool_pages_dirty';

mysql-test/suite/innodb/t/mem_pressure.test

@@ -1,5 +1,5 @@
 --source include/have_debug.inc
---source include/linux.inc
+--source include/have_cgroupv2.inc
 --source include/not_embedded.inc
 --source include/have_innodb.inc
 --source include/have_sequence.inc
@@ -33,11 +33,15 @@ WHERE VARIABLE_NAME='Innodb_buffer_pool_pages_dirty';
 set debug_dbug="d,trigger_garbage_collection";
 SET GLOBAL innodb_buffer_pool_size=@@innodb_buffer_pool_size;
 
+let SEARCH_FILE= $MYSQLTEST_VARDIR/log/mysqld.1.err;
+# either a fail or the pressure event
+let SEARCH_PATTERN= [Mm]emory pressure.*;
+--source include/search_pattern_in_file.inc
+
 SELECT CAST(VARIABLE_VALUE AS INTEGER) < @dirty_prev AS LESS_DIRTY_IS_GOOD
 FROM INFORMATION_SCHEMA.GLOBAL_STATUS
 WHERE VARIABLE_NAME='Innodb_buffer_pool_pages_dirty';
 
-let SEARCH_FILE= $MYSQLTEST_VARDIR/log/mysqld.1.err;
 let SEARCH_PATTERN= InnoDB: Memory pressure event freed.*;
 --source include/search_pattern_in_file.inc
 

storage/innobase/buf/buf0buf.cc

@@ -857,6 +857,7 @@ public:
       my_close(m_fds[m_num_fds].fd, MYF(MY_WME));
       m_fds[m_num_fds].fd= -1;
     }
+    m_event_fd= -1;
   }
 
   static void pressure_routine(mem_pressure *m);
@@ -865,10 +866,8 @@ public:
   void trigger_collection()
   {
     uint64_t u= 1;
-    if (m_event_fd >=0 && write(m_event_fd, &u, sizeof(uint64_t)) != sizeof(uint64_t))
+    if (m_event_fd < 0 || write(m_event_fd, &u, sizeof(uint64_t)) != sizeof(uint64_t))
       sql_print_information("InnoDB: (Debug) Failed to trigger memory pressure");
-    else /* assumed failed to meet intialization criteria, so trigger directy */
-      buf_pool.garbage_collect();
   }
 #endif
 
@@ -927,7 +926,7 @@ void mem_pressure::pressure_routine(mem_pressure *m)
       else
         break;
     }
-    if (!m->m_abort)
+    if (m->m_abort)
       break;
 
     for (pollfd &p : st_::span<pollfd>(m->m_fds, m->m_num_fds))