Ideas for improving Concurrency Tests - Mailing list pgsql-hackers

<div class="WordSection1"><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Ideas
forimproving Concurrency testing                               <br /><br /></span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">1.Synchronization points in server code - To have better
controlfor concurrency testing, define synchronization points in server code which can be used as follows: <br />     
                             <br />                                    heap_truncate(..) <br />                       
           { <br />                                        .... <br />                                    <br />       
                           SYNC_POINT(procid,'before_heap_open') <br />                                    rel =
heap_open(rid,AccessExclusiveLock); <br />                                    relations = lappend(relations, rel); <br
/>                                   } <br />                                <br />                                   
exec_simple_query(..)<br />                                    { <br />                                        ...    
                               <br />                                            finish_xact_command(); <br />         
                                 SYNC_POINT(procid,'finish_xact_command') <br /><br />                                 
     /* <br />                                         * If there were no parsetrees, return EmptyQueryResponse
message.<br />                                         */ <br />                                         if
(!parsetree_list)<br />                                            NullCommand(dest); <br />                           
            ... <br />                                     }   <br />                                          <br
/><br/>                                    <br />                                    When code reaches at sync point it
caneither emit a signal <br />                                    or wait for a signal <br />                         
         <br />                                    Signal <br />                                    A value of a shared
memoryvariable that will be interpretted by different <br />                                    SYNC POINTS based on
it'svalue. <br />                                    <br />                                    Emit a signal <br />   
                               Assign the value (the signal) to the shared memory variable ("set a flag") and <br />   
                               broadcast a global condition to wake those waiting for a signal. <br />                 
                 <br />                                    Wait for a signal <br />                                   
Loopover waiting for the global condition until the global value matches <br />                                    the
wait-forsignal <br /><br />                       To activate Synchronization points appropriate actions can be set.
<br/>                       For Example, <br />                            SET SYNC_POINT = 'before_heap_open WAIT_FOR
commit';<br />                            SET SYNC_POINT = 'after_finish_xact_command SIGNAL commit'; <br />           
               <br />                       This above commands can activate the synchronization points named
'before_heap_open'<br />                       and 'after_finish_xact_command'. <br />                        <br />   
                   <br />                       session "s1" <br />                       step s11  {SET SYNC_POINT =
'before_heap_openWAIT_FOR commit';} <br />                       step s12  {Truncate tbl;} <br />                     
 session"s2" <br />                       step s21  {SET SYNC_POINT = 'after_finish_xact_command SIGNAL commit';} <br
/>                      step s22  {Insert into tbl values(1);} <br />                        <br />                   
  The first activation requests the synchronization point to wait for <br />                       another backend to
emitthe signal 'commit', and second activation requests <br />                       the synchronization point to emit
thesignal 'commit', when the process's execution runs through <br />                       the synchronization point.
<br/>                        <br />                       Above defined test will allow Truncate table to wait for
Insertto finish <br /><br />2. Enhance Isolation Framework - Currently, at most one step can be waiting at a time.
EnhanceConcurrency test framework (isolation tester) to make multiple sessions wait and then allow to release it
serially.</span><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">                 
                               This might help in generating complex dead lock scenario's.</span><p
class="MsoNormal"><spanstyle="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Aboveideas could be useful to improve concurrency testing and
canalso be helpful to generate test cases for some of the complicated bugs for which there is no direct test.</span><p
class="MsoNormal"><spanstyle="font-size:10.0pt;font-family:"Arial","sans-serif"">This work is not a patch for 9.3, I
justwanted an initial feedback. </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Feedback/Suggestions?</span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Reference: <a
href="http://dev.mysql.com/doc/internals/en/debug-sync-facility.html">http://dev.mysql.com/doc/internals/en/debug-sync-facility.html</a></span><p
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style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">WithRegards,</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">AmitKapila.</span></div>