pike.git/ lib/ modules/ Sql.pmod/ pgsql_util.pmod

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2020-05-16

2020-05-16 17:25:42 by Stephen R. van den Berg <srb@cuci.nl>

pgsql: Avoid a closemux mutex race in parallel queries.

138:    * tradeoff.    */   private Regexp execfetchlimit -  = iregexp("^\a*((UPDA|DELE)TE|INSERT)\a|\aLIMIT\a+[1-9][; \t\f\r\n]*$"); +  = iregexp("^\a*((UPDA|DELE)TE|INSERT" +  "|RESET|CLOSE|DISCARD)\a|\aLIMIT\a+[1-9][; \t\f\r\n]*$");      private void default_backend_runs() { // Runs as soon as the    cb_backend = Pike.DefaultBackend; // DefaultBackend has started
300:    return realbuffer->stashcount;    }    -  final bufcon start(void|int waitforreal) { -  dirty = realbuffer->stashcount->acquire(); +  final MUTEX `shortmux() { +  return realbuffer->shortmux; +  } +  +  final bufcon start(void|int|array(Thread.MutexKey) waitforreal) { +  dirty = stashcount->acquire();   #ifdef PG_DEBUG    if (waitforreal)    error("pgsql.bufcon not allowed here\n");
310:    }       final void sendcmd(int mode, void|sql_result portal) { -  Thread.MutexKey lock = realbuffer->shortmux->lock(); +  Thread.MutexKey lock = shortmux->lock();    if (portal)    realbuffer->stashqueue->write(portal);    if (mode == SYNCSEND) {
323:    realbuffer->socket->query_fd(), mode, realbuffer->stashflushmode);    if (mode > realbuffer->stashflushmode)    realbuffer->stashflushmode = mode; +  dirty = 0; // Countdown before releasing the lock    lock = 0; -  dirty = 0; +     this->clear();    if (lock = realbuffer->nostash->trylock(1)) {   #ifdef PG_DEBUGRACE
462:    portal._portalname, ++queueoutidx, synctransact, sizeof(this));    }    -  final bufcon|conxsess start(void|int waitforreal) { +  final bufcon|conxsess start(void|int|array(Thread.MutexKey) waitforreal) {    Thread.MutexKey lock;   #ifdef PG_DEBUGRACE    if (nostash->current_locking_thread())    PD("Nostash locked by %s\n",    describe_backtrace(nostash->current_locking_thread()->backtrace()));   #endif -  while (lock = (waitforreal > 0 ? nostash->lock : nostash->trylock)(1)) { +  while (lock = (intp(waitforreal) && waitforreal > 0 +  ? nostash->lock : nostash->trylock)(1)) {    int mode;    if (sizeof(stash) && (mode = getstash(KEEP)) > KEEP)    sendcmd(mode); // Force out stash to the server    if (!stashcount->drained()) {    lock = 0; // Unlock while we wait -  +  if (arrayp(waitforreal)) +  waitforreal[0] = 0;    stashcount->wait_till_drained(); -  +  if (arrayp(waitforreal)) +  return 0;    continue; // Try again    }   #ifdef PG_DEBUGRACE
488:    return this;   #endif    } +  if (arrayp(waitforreal)) +  waitforreal[0] = 0;    return !waitforreal && bufcon(this)->start();    }   
563:    }    Thread.MutexKey lock = shortmux->trylock();    if (lock && sizeof(this)) { -  PD("%d>Sendcmd %O\n", -  socket->query_fd(), (string)this); +  PD("%d>Sendcmd %O\n", socket->query_fd(), (string)this);    output_to(socket);    }    } while (0);
890:    {    Thread.MutexKey lock = closemux->lock();    if (_fetchlimit) { -  array reflock = ({ _fetchlimit = 0 }); +  array(Thread.MutexKey) reflock = ({ _fetchlimit = 0 });    for (;;) {    reflock[0] = lock;    lock = 0;
899:    continue;    }    } -  } else +  }    lock = 0; // Force release before acquiring next    lock = _ddescribemux->lock();    if (!statuscmdcomplete)
1357:    lock = 0;    } else if (syncparse < 0 && !pgsqlsess->wasparallelisable    && !pgsqlsess->statementsinflight->drained(1)) { -  lock = 0; +  lock = 0; // Unlock while we wait    PD("Commit waiting for statements to finish\n");    catch(PT(pgsqlsess->statementsinflight->wait_till_drained(1)));    }
1389:    }       final void _parseportal() { -  { +  for (;;) {    Thread.MutexKey lock = closemux->lock(); -  _state = PARSING; -  if (syncparse || syncparse < 0 && pgsqlsess->wasparallelisable) { +  if ((syncparse || syncparse < 0 && pgsqlsess->wasparallelisable) +  && !pgsqlsess->statementsinflight->drained()) { +  lock = 0; // Unlock while we wait    PD("Commit waiting for statements to finish\n");    catch(PT(pgsqlsess->statementsinflight->wait_till_drained())); -  +  continue;    } -  +  _state = PARSING;    stmtifkey = pgsqlsess->statementsinflight->acquire(); -  +  break;    }    statuscmdcomplete = 0;    pgsqlsess->wasparallelisable = paralleliseprefix->match(_query);
1457:    _unnamedportalkey = 0;    portalsifkey = 0;    if (pgsqlsess->portalsinflight->drained()) { -  if (plugbuffer->stashcount->drained() && transtype != TRANSBEGIN) +  if (plugbuffer->stashcount->drained() && transtype != TRANSBEGIN) {    /*    * stashcount will be non-zero if a parse request has been queued    * before the close was initiated. -  * It's a bit of a tricky race, but this check should be sufficient. +     */ -  +  Thread.MutexKey lock = plugbuffer->shortmux->lock(); +  if (plugbuffer->stashcount->drained())    pgsqlsess->readyforquerycount++, retval = SYNCSEND; -  +  }    pgsqlsess->pportalcount = 0;    }    }
1483:    * index / bytesreceived || 1, _fetchlimit);    if (_fetchlimit)    if (inflight <= (_fetchlimit - 1) >> 1) { -  array reflock = ({ lock }); +  array(Thread.MutexKey) reflock = ({ lock });    lock = 0;    if (!_sendexecute(_fetchlimit, reflock))    continue;
1530:    }    inflight = 0;    conxsess plugbuffer; -  array(Thread.MutexKey) reflock = ({closemux->lock()}); -  if (!catch(plugbuffer = c->start())) +  array(Thread.MutexKey) reflock = ({ 0 }); +  for (;;) { +  reflock[0] = closemux->lock(); +  if (!catch(plugbuffer = c->start(reflock))) { +  if (plugbuffer)    plugbuffer->sendcmd(_closeportal(plugbuffer, reflock)); -  +  else +  continue; +  } +  break; +  }    reflock[0] = 0;    if (_state < CLOSED) {    stmtifkey = 0;
1556:    fetchlimit, transtype);    if (arrayp(plugbuffer)) {    reflock = plugbuffer; -  if (!(plugbuffer = c->start(-1))) { -  reflock[0] = 0; +  if (!(plugbuffer = c->start(reflock)))    return 0; // Found potential deadlock, release and try again    } -  } +     CHAIN(plugbuffer)->add_int8('E')->add_hstring(({_portalname, 0}), 4, 8)    ->add_int32(fetchlimit);    if (!fetchlimit) {
2231:   #endif    readyforquerycount--;    function (:void) cb; +  destruct(waitforauthready);    if (cb = readyforquery_cb)    readyforquery_cb = 0, cb(); -  destruct(waitforauthready); +     break;    }    case '1':