debug_sync.cc

/* Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */

#include "debug_sync.h"

#if defined(ENABLED_DEBUG_SYNC)

/*
  Due to weaknesses in our include files, we need to include
  sql_priv.h here. To have THD declared, we need to include
  sql_class.h. This includes log_event.h, which in turn requires
  declarations from sql_priv.h (e.g. OPTION_AUTO_IS_NULL).
  sql_priv.h includes almost everything, so is sufficient here.
*/
#include "sql_priv.h"
#include "sql_parse.h"

using std::max;
using std::min;

/*
  Action to perform at a synchronization point.
  NOTE: This structure is moved around in memory by realloc(), qsort(),
        and memmove(). Do not add objects with non-trivial constuctors
        or destructors, which might prevent moving of this structure
        with these functions.
*/
struct st_debug_sync_action
{
  ulong         activation_count;       /* max(hit_limit, execute) */
  ulong         hit_limit;              /* hits before kill query */
  ulong         execute;                /* executes before self-clear */
  ulong         timeout;                /* wait_for timeout */
  String        signal;                 /* signal to emit */
  String        wait_for;               /* signal to wait for */
  String        sync_point;             /* sync point name */
  bool          need_sort;              /* if new action, array needs sort */
};

/* Debug sync control. Referenced by THD. */
struct st_debug_sync_control
{
  st_debug_sync_action  *ds_action;             /* array of actions */
  uint                  ds_active;              /* # active actions */
  uint                  ds_allocated;           /* # allocated actions */
  ulonglong             dsp_hits;               /* statistics */
  ulonglong             dsp_executed;           /* statistics */
  ulonglong             dsp_max_active;         /* statistics */
  /*
    thd->proc_info points at unsynchronized memory.
    It must not go away as long as the thread exists.
  */
  char                  ds_proc_info[80];       /* proc_info string */
};


struct st_debug_sync_globals
{
  String                ds_signal;              /* signal variable */
  mysql_cond_t          ds_cond;                /* condition variable */
  mysql_mutex_t         ds_mutex;               /* mutex variable */
  ulonglong             dsp_hits;               /* statistics */
  ulonglong             dsp_executed;           /* statistics */
  ulonglong             dsp_max_active;         /* statistics */
};
static st_debug_sync_globals debug_sync_global; /* All globals in one object */

extern "C" void (*debug_sync_C_callback_ptr)(const char *, size_t);

C_MODE_START
static void debug_sync_C_callback(const char *, size_t);
static int debug_sync_qsort_cmp(const void *, const void *);
C_MODE_END

static void debug_sync_C_callback(const char *sync_point_name,
                                  size_t name_len)
{
  if (unlikely(opt_debug_sync_timeout))
    debug_sync(current_thd, sync_point_name, name_len);
}

#ifdef HAVE_PSI_INTERFACE
static PSI_mutex_key key_debug_sync_globals_ds_mutex;

static PSI_mutex_info all_debug_sync_mutexes[]=
{
  { &key_debug_sync_globals_ds_mutex, "DEBUG_SYNC::mutex", PSI_FLAG_GLOBAL}
};

static PSI_cond_key key_debug_sync_globals_ds_cond;

static PSI_cond_info all_debug_sync_conds[]=
{
  { &key_debug_sync_globals_ds_cond, "DEBUG_SYNC::cond", PSI_FLAG_GLOBAL}
};

static void init_debug_sync_psi_keys(void)
{
  const char* category= "sql";
  int count;

  count= array_elements(all_debug_sync_mutexes);
  mysql_mutex_register(category, all_debug_sync_mutexes, count);

  count= array_elements(all_debug_sync_conds);
  mysql_cond_register(category, all_debug_sync_conds, count);
}
#endif /* HAVE_PSI_INTERFACE */


int debug_sync_init(void)
{
  DBUG_ENTER("debug_sync_init");

#ifdef HAVE_PSI_INTERFACE
  init_debug_sync_psi_keys();
#endif

  if (opt_debug_sync_timeout)
  {
    int rc;

    /* Initialize the global variables. */
    debug_sync_global.ds_signal.length(0);
    if ((rc= mysql_cond_init(key_debug_sync_globals_ds_cond,
                             &debug_sync_global.ds_cond, NULL)) ||
        (rc= mysql_mutex_init(key_debug_sync_globals_ds_mutex,
                              &debug_sync_global.ds_mutex,
                              MY_MUTEX_INIT_FAST)))
      DBUG_RETURN(rc); /* purecov: inspected */

    /* Set the call back pointer in C files. */
    debug_sync_C_callback_ptr= debug_sync_C_callback;
  }

  DBUG_RETURN(0);
}


void debug_sync_end(void)
{
  DBUG_ENTER("debug_sync_end");

  /* End the facility only if it had been initialized. */
  if (debug_sync_C_callback_ptr)
  {
    /* Clear the call back pointer in C files. */
    debug_sync_C_callback_ptr= NULL;

    /* Destroy the global variables. */
    debug_sync_global.ds_signal.free();
    mysql_cond_destroy(&debug_sync_global.ds_cond);
    mysql_mutex_destroy(&debug_sync_global.ds_mutex);

    /* Print statistics. */
    {
      char llbuff[22];
      sql_print_information("Debug sync points hit:                   %22s",
                            llstr(debug_sync_global.dsp_hits, llbuff));
      sql_print_information("Debug sync points executed:              %22s",
                            llstr(debug_sync_global.dsp_executed, llbuff));
      sql_print_information("Debug sync points max active per thread: %22s",
                            llstr(debug_sync_global.dsp_max_active, llbuff));
    }
  }

  DBUG_VOID_RETURN;
}


/* purecov: begin tested */

static void debug_sync_emergency_disable(void)
{
  DBUG_ENTER("debug_sync_emergency_disable");

  opt_debug_sync_timeout= 0;

  DBUG_PRINT("debug_sync",
             ("Debug Sync Facility disabled due to lack of memory."));
  sql_print_error("Debug Sync Facility disabled due to lack of memory.");

  DBUG_VOID_RETURN;
}

/* purecov: end */


void debug_sync_init_thread(THD *thd)
{
  DBUG_ENTER("debug_sync_init_thread");
  DBUG_ASSERT(thd);

  if (opt_debug_sync_timeout)
  {
    thd->debug_sync_control= (st_debug_sync_control*)
      my_malloc(sizeof(st_debug_sync_control), MYF(MY_WME | MY_ZEROFILL));
    if (!thd->debug_sync_control)
    {
      /*
        Error is reported by my_malloc().
        We must disable the facility. We have no way to return an error.
      */
      debug_sync_emergency_disable(); /* purecov: tested */
    }
  }

  DBUG_VOID_RETURN;
}


void debug_sync_end_thread(THD *thd)
{
  DBUG_ENTER("debug_sync_end_thread");
  DBUG_ASSERT(thd);

  if (thd->debug_sync_control)
  {
    st_debug_sync_control *ds_control= thd->debug_sync_control;

    /*
      This synchronization point can be used to synchronize on thread end.
      This is the latest point in a THD's life, where this can be done.
    */
    DEBUG_SYNC(thd, "thread_end");

    if (ds_control->ds_action)
    {
      st_debug_sync_action *action= ds_control->ds_action;
      st_debug_sync_action *action_end= action + ds_control->ds_allocated;
      for (; action < action_end; action++)
      {
        action->signal.free();
        action->wait_for.free();
        action->sync_point.free();
      }
      my_free(ds_control->ds_action);
    }

    /* Statistics. */
    mysql_mutex_lock(&debug_sync_global.ds_mutex);
    debug_sync_global.dsp_hits+=           ds_control->dsp_hits;
    debug_sync_global.dsp_executed+=       ds_control->dsp_executed;
    if (debug_sync_global.dsp_max_active < ds_control->dsp_max_active)
      debug_sync_global.dsp_max_active=    ds_control->dsp_max_active;
    mysql_mutex_unlock(&debug_sync_global.ds_mutex);

    my_free(ds_control);
    thd->debug_sync_control= NULL;
  }

  DBUG_VOID_RETURN;
}


static char *debug_sync_bmove_len(char *to, char *to_end,
                                  const char *from, size_t length)
{
  DBUG_ASSERT(to);
  DBUG_ASSERT(to_end);
  DBUG_ASSERT(!length || from);
  set_if_smaller(length, (size_t) (to_end - to));
  memcpy(to, from, length);
  return (to + length);
}


#if !defined(DBUG_OFF)

static void debug_sync_action_string(char *result, uint size,
                                     st_debug_sync_action *action)
{
  char  *wtxt= result;
  char  *wend= wtxt + size - 1; /* Allow emergency '\0'. */
  DBUG_ASSERT(result);
  DBUG_ASSERT(action);

  /* If an execute count is present, signal or wait_for are needed too. */
  DBUG_ASSERT(!action->execute ||
              action->signal.length() || action->wait_for.length());

  if (action->execute)
  {
    if (action->signal.length())
    {
      wtxt= debug_sync_bmove_len(wtxt, wend, STRING_WITH_LEN("SIGNAL "));
      wtxt= debug_sync_bmove_len(wtxt, wend, action->signal.ptr(),
                                 action->signal.length());
    }
    if (action->wait_for.length())
    {
      if ((wtxt == result) && (wtxt < wend))
        *(wtxt++)= ' ';
      wtxt= debug_sync_bmove_len(wtxt, wend, STRING_WITH_LEN(" WAIT_FOR "));
      wtxt= debug_sync_bmove_len(wtxt, wend, action->wait_for.ptr(),
                                 action->wait_for.length());

      if (action->timeout != opt_debug_sync_timeout)
      {
        wtxt+= my_snprintf(wtxt, wend - wtxt, " TIMEOUT %lu", action->timeout);
      }
    }
    if (action->execute != 1)
    {
      wtxt+= my_snprintf(wtxt, wend - wtxt, " EXECUTE %lu", action->execute);
    }
  }
  if (action->hit_limit)
  {
    wtxt+= my_snprintf(wtxt, wend - wtxt, "%sHIT_LIMIT %lu",
                       (wtxt == result) ? "" : " ", action->hit_limit);
  }

  /*
    If (wtxt == wend) string may not be terminated.
    There is one byte left for an emergency termination.
  */
  *wtxt= '\0';
}


static void debug_sync_print_actions(THD *thd)
{
  st_debug_sync_control *ds_control= thd->debug_sync_control;
  uint                  idx;
  DBUG_ENTER("debug_sync_print_actions");
  DBUG_ASSERT(thd);

  if (!ds_control)
    DBUG_VOID_RETURN;

  for (idx= 0; idx < ds_control->ds_active; idx++)
  {
    const char *dsp_name= ds_control->ds_action[idx].sync_point.c_ptr();
    char action_string[256];

    debug_sync_action_string(action_string, sizeof(action_string),
                             ds_control->ds_action + idx);
    DBUG_PRINT("debug_sync_list", ("%s %s", dsp_name, action_string));
  }

  DBUG_VOID_RETURN;
}

#endif /* !defined(DBUG_OFF) */


static int debug_sync_qsort_cmp(const void* arg1, const void* arg2)
{
  st_debug_sync_action *action1= (st_debug_sync_action*) arg1;
  st_debug_sync_action *action2= (st_debug_sync_action*) arg2;
  int diff;
  DBUG_ASSERT(action1);
  DBUG_ASSERT(action2);

  if (!(diff= action1->sync_point.length() - action2->sync_point.length()))
    diff= memcmp(action1->sync_point.ptr(), action2->sync_point.ptr(),
                 action1->sync_point.length());

  return diff;
}


static st_debug_sync_action *debug_sync_find(st_debug_sync_action *actionarr,
                                             int quantity,
                                             const char *dsp_name,
                                             uint name_len)
{
  st_debug_sync_action  *action;
  int                   low ;
  int                   high ;
  int                   mid ;
  int                   diff ;
  DBUG_ASSERT(actionarr);
  DBUG_ASSERT(dsp_name);
  DBUG_ASSERT(name_len);

  low= 0;
  high= quantity;

  while (low < high)
  {
    mid= (low + high) / 2;
    action= actionarr + mid;
    if (!(diff= name_len - action->sync_point.length()) &&
        !(diff= memcmp(dsp_name, action->sync_point.ptr(), name_len)))
      return action;
    if (diff > 0)
      low= mid + 1;
    else
      high= mid - 1;
  }

  if (low < quantity)
  {
    action= actionarr + low;
    if ((name_len == action->sync_point.length()) &&
        !memcmp(dsp_name, action->sync_point.ptr(), name_len))
      return action;
  }

  return NULL;
}


static void debug_sync_reset(THD *thd)
{
  st_debug_sync_control *ds_control= thd->debug_sync_control;
  DBUG_ENTER("debug_sync_reset");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(ds_control);

  /* Remove all actions of this thread. */
  ds_control->ds_active= 0;

  /* Clear the global signal. */
  mysql_mutex_lock(&debug_sync_global.ds_mutex);
  debug_sync_global.ds_signal.length(0);
  mysql_mutex_unlock(&debug_sync_global.ds_mutex);

  DBUG_VOID_RETURN;
}


static void debug_sync_remove_action(st_debug_sync_control *ds_control,
                                     st_debug_sync_action *action)
{
  uint dsp_idx= action - ds_control->ds_action;
  DBUG_ENTER("debug_sync_remove_action");
  DBUG_ASSERT(ds_control);
  DBUG_ASSERT(ds_control == current_thd->debug_sync_control);
  DBUG_ASSERT(action);
  DBUG_ASSERT(dsp_idx < ds_control->ds_active);

  /* Decrement the number of currently active actions. */
  ds_control->ds_active--;

  /*
    If this was not the last active action in the array, we need to
    shift remaining active actions down to keep the array gap-free.
    Otherwise binary search might fail or take longer than necessary at
    least. Also new actions are always put to the end of the array.
  */
  if (ds_control->ds_active > dsp_idx)
  {
    /*
      Do not make save_action an object of class st_debug_sync_action.
      Its destructor would tamper with the String pointers.
    */
    uchar save_action[sizeof(st_debug_sync_action)];

    /*
      Copy the to-be-removed action object to temporary storage before
      the shift copies the string pointers over. Do not use assignment
      because it would use assignment operator methods for the Strings.
      This would copy the strings. The shift below overwrite the string
      pointers without freeing them first. By using memmove() we save
      the pointers, which are overwritten by the shift.
    */
    memmove(save_action, action, sizeof(st_debug_sync_action));

    /* Move actions down. */
    memmove(ds_control->ds_action + dsp_idx,
            ds_control->ds_action + dsp_idx + 1,
            (ds_control->ds_active - dsp_idx) *
            sizeof(st_debug_sync_action));

    /*
      Copy back the saved action object to the now free array slot. This
      replaces the double references of String pointers that have been
      produced by the shift. Again do not use an assignment operator to
      avoid string allocation/copy.
    */
    memmove(ds_control->ds_action + ds_control->ds_active, save_action,
            sizeof(st_debug_sync_action));
  }

  DBUG_VOID_RETURN;
}


static st_debug_sync_action *debug_sync_get_action(THD *thd,
                                                   const char *dsp_name,
                                                   uint name_len)
{
  st_debug_sync_control *ds_control= thd->debug_sync_control;
  st_debug_sync_action  *action;
  DBUG_ENTER("debug_sync_get_action");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(dsp_name);
  DBUG_ASSERT(name_len);
  DBUG_ASSERT(ds_control);
  DBUG_PRINT("debug_sync", ("sync_point: '%.*s'", (int) name_len, dsp_name));
  DBUG_PRINT("debug_sync", ("active: %u  allocated: %u",
                            ds_control->ds_active, ds_control->ds_allocated));

  /* There cannot be more active actions than allocated. */
  DBUG_ASSERT(ds_control->ds_active <= ds_control->ds_allocated);
  /* If there are active actions, the action array must be present. */
  DBUG_ASSERT(!ds_control->ds_active || ds_control->ds_action);

  /* Try to reuse existing action if there is one for this sync point. */
  if (ds_control->ds_active &&
      (action= debug_sync_find(ds_control->ds_action, ds_control->ds_active,
                               dsp_name, name_len)))
  {
    /* Reuse an already active sync point action. */
    DBUG_ASSERT((uint)(action - ds_control->ds_action) < ds_control->ds_active);
    DBUG_PRINT("debug_sync", ("reuse action idx: %ld",
                              (long) (action - ds_control->ds_action)));
  }
  else
  {
    /* Create a new action. */
    int dsp_idx= ds_control->ds_active++;
    set_if_bigger(ds_control->dsp_max_active, ds_control->ds_active);
    if (ds_control->ds_active > ds_control->ds_allocated)
    {
      uint new_alloc= ds_control->ds_active + 3;
      void *new_action= my_realloc(ds_control->ds_action,
                                   new_alloc * sizeof(st_debug_sync_action),
                                   MYF(MY_WME | MY_ALLOW_ZERO_PTR));
      if (!new_action)
      {
        /* Error is reported by my_malloc(). */
        goto err; /* purecov: tested */
      }
      ds_control->ds_action= (st_debug_sync_action*) new_action;
      ds_control->ds_allocated= new_alloc;
      /* Clear memory as we do not run string constructors here. */
      memset((ds_control->ds_action + dsp_idx), 0,
            (new_alloc - dsp_idx) * sizeof(st_debug_sync_action));
    }
    DBUG_PRINT("debug_sync", ("added action idx: %u", dsp_idx));
    action= ds_control->ds_action + dsp_idx;
    if (action->sync_point.copy(dsp_name, name_len, system_charset_info))
    {
      /* Error is reported by my_malloc(). */
      goto err; /* purecov: tested */
    }
    action->need_sort= TRUE;
  }
  DBUG_ASSERT(action >= ds_control->ds_action);
  DBUG_ASSERT(action < ds_control->ds_action + ds_control->ds_active);
  DBUG_PRINT("debug_sync", ("action: 0x%lx  array: 0x%lx  count: %u",
                            (long) action, (long) ds_control->ds_action,
                            ds_control->ds_active));

  DBUG_RETURN(action);

  /* purecov: begin tested */
 err:
  DBUG_RETURN(NULL);
  /* purecov: end */
}


static bool debug_sync_set_action(THD *thd, st_debug_sync_action *action)
{
  st_debug_sync_control *ds_control= thd->debug_sync_control;
  bool is_dsp_now= FALSE;
  DBUG_ENTER("debug_sync_set_action");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(action);
  DBUG_ASSERT(ds_control);

  action->activation_count= max(action->hit_limit, action->execute);
  if (!action->activation_count)
  {
    debug_sync_remove_action(ds_control, action);
    DBUG_PRINT("debug_sync", ("action cleared"));
  }
  else
  {
    const char *dsp_name= action->sync_point.c_ptr();
    DBUG_EXECUTE("debug_sync", {
        /* Functions as DBUG_PRINT args can change keyword and line nr. */
        const char *sig_emit= action->signal.c_ptr();
        const char *sig_wait= action->wait_for.c_ptr();
        DBUG_PRINT("debug_sync",
                   ("sync_point: '%s'  activation_count: %lu  hit_limit: %lu  "
                    "execute: %lu  timeout: %lu  signal: '%s'  wait_for: '%s'",
                    dsp_name, action->activation_count,
                    action->hit_limit, action->execute, action->timeout,
                    sig_emit, sig_wait));});

    /* Check this before sorting the array. action may move. */
    is_dsp_now= !my_strcasecmp(system_charset_info, dsp_name, "now");

    if (action->need_sort)
    {
      action->need_sort= FALSE;
      /* Sort actions by (name_len, name). */
      my_qsort(ds_control->ds_action, ds_control->ds_active,
               sizeof(st_debug_sync_action), debug_sync_qsort_cmp);
    }
  }
  DBUG_EXECUTE("debug_sync_list", debug_sync_print_actions(thd););

  /* Execute the special sync point 'now' if activated above. */
  if (is_dsp_now)
  {
    DEBUG_SYNC(thd, "now");
    /*
      If HIT_LIMIT for sync point "now" was 1, the execution of the sync
      point decremented it to 0. In this case the following happened:

      - an error message was reported with my_error() and
      - the statement was killed with thd->killed= THD::KILL_QUERY.

      If a statement reports an error, it must not call send_ok().
      The calling functions will not call send_ok(), if we return TRUE
      from this function.

      thd->killed is also set if the wait is interrupted from a
      KILL or KILL QUERY statement. In this case, no error is reported
      and shall not be reported as a result of SET DEBUG_SYNC.
      Hence, we check for the first condition above.
    */
    if (thd->is_error())
      DBUG_RETURN(TRUE);
  }

  DBUG_RETURN(FALSE);
}


static char *debug_sync_token(char **token_p, uint *token_length_p, char *ptr)
{
  DBUG_ASSERT(token_p);
  DBUG_ASSERT(token_length_p);
  DBUG_ASSERT(ptr);

  /* Skip leading space */
  while (my_isspace(system_charset_info, *ptr))
    ptr+= my_mbcharlen(system_charset_info, (uchar) *ptr);

  if (!*ptr)
  {
    ptr= NULL;
    goto end;
  }

  /* Get token start. */
  *token_p= ptr;

  /* Find token end. */
  while (*ptr && !my_isspace(system_charset_info, *ptr))
    ptr+= my_mbcharlen(system_charset_info, (uchar) *ptr);

  /* Get token length. */
  *token_length_p= ptr - *token_p;

  /* If necessary, terminate token. */
  if (*ptr)
  {
    /* Get terminator character length. */
    uint mbspacelen= my_mbcharlen(system_charset_info, (uchar) *ptr);

    /* Terminate token. */
    *ptr= '\0';

    /* Skip the terminator. */
    ptr+= mbspacelen;

    /* Skip trailing space */
    while (my_isspace(system_charset_info, *ptr))
      ptr+= my_mbcharlen(system_charset_info, (uchar) *ptr);
  }

 end:
  return ptr;
}


static char *debug_sync_number(ulong *number_p, char *actstrptr)
{
  char                  *ptr;
  char                  *ept;
  char                  *token;
  uint                  token_length;
  DBUG_ASSERT(number_p);
  DBUG_ASSERT(actstrptr);

  /* Get token from string. */
  if (!(ptr= debug_sync_token(&token, &token_length, actstrptr)))
    goto end;

  *number_p= strtoul(token, &ept, 10);
  if (*ept)
    ptr= NULL;

 end:
  return ptr;
}


static bool debug_sync_eval_action(THD *thd, char *action_str)
{
  st_debug_sync_action  *action= NULL;
  const char            *errmsg;
  char                  *ptr;
  char                  *token;
  uint                  token_length= 0;
  DBUG_ENTER("debug_sync_eval_action");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(action_str);

  /*
    Get debug sync point name. Or a special command.
  */
  if (!(ptr= debug_sync_token(&token, &token_length, action_str)))
  {
    errmsg= "Missing synchronization point name";
    goto err;
  }

  /*
    If there is a second token, the first one is the sync point name.
  */
  if (*ptr)
  {
    /* Get an action object to collect the requested action parameters. */
    action= debug_sync_get_action(thd, token, token_length);
    if (!action)
    {
      /* Error message is sent. */
      DBUG_RETURN(TRUE); /* purecov: tested */
    }
  }

  /*
    Get kind of action to be taken at sync point.
  */
  if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
  {
    /* No action present. Try special commands. Token unchanged. */

    /*
      Try RESET.
    */
    if (!my_strcasecmp(system_charset_info, token, "RESET"))
    {
      /* It is RESET. Reset all actions and global signal. */
      debug_sync_reset(thd);
      goto end;
    }

    /* Token unchanged. It still contains sync point name. */
    errmsg= "Missing action after synchronization point name '%.*s'";
    goto err;
  }

  /*
    Check for pseudo actions first. Start with actions that work on
    an existing action.
  */
  DBUG_ASSERT(action);

  /*
    Try TEST.
  */
  if (!my_strcasecmp(system_charset_info, token, "TEST"))
  {
    /* It is TEST. Nothing must follow it. */
    if (*ptr)
    {
      errmsg= "Nothing must follow action TEST";
      goto err;
    }

    /* Execute sync point. */
    debug_sync(thd, action->sync_point.ptr(), action->sync_point.length());
    /* Fix statistics. This was not a real hit of the sync point. */
    thd->debug_sync_control->dsp_hits--;
    goto end;
  }

  /*
    Now check for actions that define a new action.
    Initialize action. Do not use memset(). Strings may have malloced.
  */
  action->activation_count= 0;
  action->hit_limit= 0;
  action->execute= 0;
  action->timeout= 0;
  action->signal.length(0);
  action->wait_for.length(0);

  /*
    Try CLEAR.
  */
  if (!my_strcasecmp(system_charset_info, token, "CLEAR"))
  {
    /* It is CLEAR. Nothing must follow it. */
    if (*ptr)
    {
      errmsg= "Nothing must follow action CLEAR";
      goto err;
    }

    /* Set (clear/remove) action. */
    goto set_action;
  }

  /*
    Now check for real sync point actions.
  */

  /*
    Try SIGNAL.
  */
  if (!my_strcasecmp(system_charset_info, token, "SIGNAL"))
  {
    /* It is SIGNAL. Signal name must follow. */
    if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
    {
      errmsg= "Missing signal name after action SIGNAL";
      goto err;
    }
    if (action->signal.copy(token, token_length, system_charset_info))
    {
      /* Error is reported by my_malloc(). */
      /* purecov: begin tested */
      errmsg= NULL;
      goto err;
      /* purecov: end */
    }

    /* Set default for EXECUTE option. */
    action->execute= 1;

    /* Get next token. If none follows, set action. */
    if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
      goto set_action;
  }

  /*
    Try WAIT_FOR.
  */
  if (!my_strcasecmp(system_charset_info, token, "WAIT_FOR"))
  {
    /* It is WAIT_FOR. Wait_for signal name must follow. */
    if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
    {
      errmsg= "Missing signal name after action WAIT_FOR";
      goto err;
    }
    if (action->wait_for.copy(token, token_length, system_charset_info))
    {
      /* Error is reported by my_malloc(). */
      /* purecov: begin tested */
      errmsg= NULL;
      goto err;
      /* purecov: end */
    }

    /* Set default for EXECUTE and TIMEOUT options. */
    action->execute= 1;
    action->timeout= opt_debug_sync_timeout;

    /* Get next token. If none follows, set action. */
    if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
      goto set_action;

    /*
      Try TIMEOUT.
    */
    if (!my_strcasecmp(system_charset_info, token, "TIMEOUT"))
    {
      /* It is TIMEOUT. Number must follow. */
      if (!(ptr= debug_sync_number(&action->timeout, ptr)))
      {
        errmsg= "Missing valid number after TIMEOUT";
        goto err;
      }

      /* Get next token. If none follows, set action. */
      if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
        goto set_action;
    }
  }

  /*
    Try EXECUTE.
  */
  if (!my_strcasecmp(system_charset_info, token, "EXECUTE"))
  {
    /*
      EXECUTE requires either SIGNAL and/or WAIT_FOR to be present.
      In this case action->execute has been preset to 1.
    */
    if (!action->execute)
    {
      errmsg= "Missing action before EXECUTE";
      goto err;
    }

    /* Number must follow. */
    if (!(ptr= debug_sync_number(&action->execute, ptr)))
    {
      errmsg= "Missing valid number after EXECUTE";
      goto err;
    }

    /* Get next token. If none follows, set action. */
    if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
      goto set_action;
  }

  /*
    Try HIT_LIMIT.
  */
  if (!my_strcasecmp(system_charset_info, token, "HIT_LIMIT"))
  {
    /* Number must follow. */
    if (!(ptr= debug_sync_number(&action->hit_limit, ptr)))
    {
      errmsg= "Missing valid number after HIT_LIMIT";
      goto err;
    }

    /* Get next token. If none follows, set action. */
    if (!(ptr= debug_sync_token(&token, &token_length, ptr)))
      goto set_action;
  }

  errmsg= "Illegal or out of order stuff: '%.*s'";

 err:
  if (errmsg)
  {
    /*
      NOTE: errmsg must either have %.*s or none % at all.
      It can be NULL if an error message is already reported
      (e.g. by my_malloc()).
    */
    set_if_smaller(token_length, 64); /* Limit error message length. */
    my_printf_error(ER_PARSE_ERROR, errmsg, MYF(0), token_length, token);
  }
  if (action)
    debug_sync_remove_action(thd->debug_sync_control, action);
  DBUG_RETURN(TRUE);

 set_action:
  DBUG_RETURN(debug_sync_set_action(thd, action));

 end:
  DBUG_RETURN(FALSE);
}

bool debug_sync_update(THD *thd, char *val_str)
{
  DBUG_ENTER("debug_sync_update");
  DBUG_PRINT("debug_sync", ("set action: '%s'", val_str));

  /*
    debug_sync_eval_action() places '\0' in the string, which itself
    must be '\0' terminated.
  */
  DBUG_RETURN(opt_debug_sync_timeout ?
              debug_sync_eval_action(thd, val_str) :
              FALSE);
}


uchar *debug_sync_value_ptr(THD *thd)
{
  char *value;
  DBUG_ENTER("debug_sync_value_ptr");

  if (opt_debug_sync_timeout)
  {
    static char on[]= "ON - current signal: '"; 

    // Ensure exclusive access to debug_sync_global.ds_signal
    mysql_mutex_lock(&debug_sync_global.ds_mutex);

    size_t lgt= (sizeof(on) /* includes '\0' */ +
                 debug_sync_global.ds_signal.length() + 1 /* for '\'' */);
    char *vend;
    char *vptr;

    if ((value= (char*) alloc_root(thd->mem_root, lgt)))
    {
      vend= value + lgt - 1; /* reserve space for '\0'. */
      vptr= debug_sync_bmove_len(value, vend, STRING_WITH_LEN(on));
      vptr= debug_sync_bmove_len(vptr, vend, debug_sync_global.ds_signal.ptr(),
                                 debug_sync_global.ds_signal.length());
      if (vptr < vend)
        *(vptr++)= '\'';
      *vptr= '\0'; /* We have one byte reserved for the worst case. */
    }
    mysql_mutex_unlock(&debug_sync_global.ds_mutex);
  }
  else
  {
    /* purecov: begin tested */
    value= const_cast<char*>("OFF");
    /* purecov: end */
  }

  DBUG_RETURN((uchar*) value);
}


static void debug_sync_execute(THD *thd, st_debug_sync_action *action)
{
#ifndef DBUG_OFF
  const char *dsp_name= action->sync_point.c_ptr();
  const char *sig_emit= action->signal.c_ptr();
  const char *sig_wait= action->wait_for.c_ptr();
#endif
  DBUG_ENTER("debug_sync_execute");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(action);
  DBUG_PRINT("debug_sync",
             ("sync_point: '%s'  activation_count: %lu  hit_limit: %lu  "
              "execute: %lu  timeout: %lu  signal: '%s'  wait_for: '%s'",
              dsp_name, action->activation_count, action->hit_limit,
              action->execute, action->timeout, sig_emit, sig_wait));

  DBUG_ASSERT(action->activation_count);
  action->activation_count--;

  if (action->execute)
  {
    const char *UNINIT_VAR(old_proc_info);

    action->execute--;

    /*
      If we will be going to wait, set proc_info for the PROCESSLIST table.
      Do this before emitting the signal, so other threads can see it
      if they awake before we enter_cond() below.
    */
    if (action->wait_for.length())
    {
      st_debug_sync_control *ds_control= thd->debug_sync_control;
      strxnmov(ds_control->ds_proc_info, sizeof(ds_control->ds_proc_info)-1,
               "debug sync point: ", action->sync_point.c_ptr(), NullS);
      old_proc_info= thd->proc_info;
      thd_proc_info(thd, ds_control->ds_proc_info);
    }

    /*
      Take mutex to ensure that only one thread access
      debug_sync_global.ds_signal at a time.  Need to take mutex for
      read access too, to create a memory barrier in order to avoid that
      threads just reads an old cached version of the signal.
    */
    mysql_mutex_lock(&debug_sync_global.ds_mutex);

    if (action->signal.length())
    {
      /* Copy the signal to the global variable. */
      if (debug_sync_global.ds_signal.copy(action->signal))
      {
        /*
          Error is reported by my_malloc().
          We must disable the facility. We have no way to return an error.
        */
        debug_sync_emergency_disable(); /* purecov: tested */
      }
      /* Wake threads waiting in a sync point. */
      mysql_cond_broadcast(&debug_sync_global.ds_cond);
      DBUG_PRINT("debug_sync_exec", ("signal '%s'  at: '%s'",
                                     sig_emit, dsp_name));
    } /* end if (action->signal.length()) */

    if (action->wait_for.length())
    {
      mysql_mutex_t *old_mutex;
      mysql_cond_t  *old_cond= 0;
      int             error= 0;
      struct timespec abstime;

      /*
        We don't use enter_cond()/exit_cond(). They do not save old
        mutex and cond. This would prohibit the use of DEBUG_SYNC
        between other places of enter_cond() and exit_cond().

        We need to check for existence of thd->mysys_var to also make
        it possible to use DEBUG_SYNC framework in scheduler when this
        variable has been set to NULL.
      */
      if (thd->mysys_var)
      {
        old_mutex= thd->mysys_var->current_mutex;
        old_cond= thd->mysys_var->current_cond;
        thd->mysys_var->current_mutex= &debug_sync_global.ds_mutex;
        thd->mysys_var->current_cond= &debug_sync_global.ds_cond;
      }
      else
        old_mutex= NULL;

      set_timespec(abstime, action->timeout);
      DBUG_EXECUTE("debug_sync_exec", {
          /* Functions as DBUG_PRINT args can change keyword and line nr. */
          const char *sig_glob= debug_sync_global.ds_signal.c_ptr();
          DBUG_PRINT("debug_sync_exec",
                     ("wait for '%s'  at: '%s'  curr: '%s'",
                      sig_wait, dsp_name, sig_glob));});

      /*
        Wait until global signal string matches the wait_for string.
        Interrupt when thread or query is killed or facility disabled.
        The facility can become disabled when some thread cannot get
        the required dynamic memory allocated.
      */
      while (stringcmp(&debug_sync_global.ds_signal, &action->wait_for) &&
             !thd->killed && opt_debug_sync_timeout)
      {
        error= mysql_cond_timedwait(&debug_sync_global.ds_cond,
                                    &debug_sync_global.ds_mutex,
                                    &abstime);
        DBUG_EXECUTE("debug_sync", {
            /* Functions as DBUG_PRINT args can change keyword and line nr. */
            const char *sig_glob= debug_sync_global.ds_signal.c_ptr();
            DBUG_PRINT("debug_sync",
                       ("awoke from %s  global: %s  error: %d",
                        sig_wait, sig_glob, error));});
        if (error == ETIMEDOUT || error == ETIME)
        {
          // We should not make the statement fail, even if in strict mode.
          const bool save_abort_on_warning= thd->abort_on_warning;
          thd->abort_on_warning= false;
          push_warning(thd, Sql_condition::WARN_LEVEL_WARN,
                       ER_DEBUG_SYNC_TIMEOUT, ER(ER_DEBUG_SYNC_TIMEOUT));
          thd->abort_on_warning= save_abort_on_warning;
          DBUG_EXECUTE_IF("debug_sync_abort_on_timeout", DBUG_ABORT(););
          break;
        }
        error= 0;
      }
      DBUG_EXECUTE("debug_sync_exec",
                   if (thd->killed)
                     DBUG_PRINT("debug_sync_exec",
                                ("killed %d from '%s'  at: '%s'",
                                 thd->killed, sig_wait, dsp_name));
                   else
                     DBUG_PRINT("debug_sync_exec",
                                ("%s from '%s'  at: '%s'",
                                 error ? "timeout" : "resume",
                                 sig_wait, dsp_name)););

      /*
        We don't use enter_cond()/exit_cond(). They do not save old
        mutex and cond. This would prohibit the use of DEBUG_SYNC
        between other places of enter_cond() and exit_cond(). The
        protected mutex must always unlocked _before_ mysys_var->mutex
        is locked. (See comment in THD::exit_cond().)
      */
      mysql_mutex_unlock(&debug_sync_global.ds_mutex);
      if (old_mutex)
      {
        mysql_mutex_lock(&thd->mysys_var->mutex);
        thd->mysys_var->current_mutex= old_mutex;
        thd->mysys_var->current_cond= old_cond;
        thd_proc_info(thd, old_proc_info);
        mysql_mutex_unlock(&thd->mysys_var->mutex);
      }
      else
        thd_proc_info(thd, old_proc_info);
    }
    else
    {
      /* In case we don't wait, we just release the mutex. */
      mysql_mutex_unlock(&debug_sync_global.ds_mutex);
    } /* end if (action->wait_for.length()) */

  } /* end if (action->execute) */

  /* hit_limit is zero for infinite. Don't decrement unconditionally. */
  if (action->hit_limit)
  {
    if (!--action->hit_limit)
    {
      thd->killed= THD::KILL_QUERY;
      my_error(ER_DEBUG_SYNC_HIT_LIMIT, MYF(0));
    }
    DBUG_PRINT("debug_sync_exec", ("hit_limit: %lu  at: '%s'",
                                   action->hit_limit, dsp_name));
  }

  DBUG_VOID_RETURN;
}


void debug_sync(THD *thd, const char *sync_point_name, size_t name_len)
{
  if(!thd)
  {
    return;
  }

  st_debug_sync_control *ds_control= thd->debug_sync_control;
  st_debug_sync_action  *action;
  DBUG_ENTER("debug_sync");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(sync_point_name);
  DBUG_ASSERT(name_len);
  DBUG_ASSERT(ds_control);
  DBUG_PRINT("debug_sync_point", ("hit: '%s'", sync_point_name));

  /* Statistics. */
  ds_control->dsp_hits++;

  if (ds_control->ds_active &&
      (action= debug_sync_find(ds_control->ds_action, ds_control->ds_active,
                               sync_point_name, name_len)) &&
      action->activation_count)
  {
    /* Sync point is active (action exists). */
    debug_sync_execute(thd, action);

    /* Statistics. */
    ds_control->dsp_executed++;

    /* If action became inactive, remove it to shrink the search array. */
    if (!action->activation_count)
      debug_sync_remove_action(ds_control, action);
  }

  DBUG_VOID_RETURN;
}

bool debug_sync_set_action(THD *thd, const char *action_str, size_t len)
{
  bool                  rc;
  char *value;
  DBUG_ENTER("debug_sync_set_action");
  DBUG_ASSERT(thd);
  DBUG_ASSERT(action_str);
  
  value= strmake_root(thd->mem_root, action_str, len);
  rc= debug_sync_eval_action(thd, value);
  DBUG_RETURN(rc);
}


#endif /* defined(ENABLED_DEBUG_SYNC) */