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mariadb/sql/debug_sync.cc
Davi Arnaut f56dd32bf7 Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled 
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.

Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.

Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost. 

The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.

Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.

client/mysqldump.c:
  Pass my_free directly as its signature is compatible with the
  callback type -- which wasn't the case for free_table_ent.
2010-07-08 18:20:08 -03:00

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/* Copyright (C) 2008 MySQL AB, 2008 - 2009 Sun Microsystems, Inc.
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, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/**
== Debug Sync Facility ==
The Debug Sync Facility allows placement of synchronization points in
the server code by using the DEBUG_SYNC macro:
open_tables(...)
DEBUG_SYNC(thd, "after_open_tables");
lock_tables(...)
When activated, a sync point can
- Emit a signal and/or
- Wait for a signal
Nomenclature:
- signal: A value of a global variable that persists
until overwritten by a new signal. The global
variable can also be seen as a "signal post"
or "flag mast". Then the signal is what is
attached to the "signal post" or "flag mast".
- emit a signal: Assign the value (the signal) to the global
variable ("set a flag") and broadcast a
global condition to wake those waiting for
a signal.
- wait for a signal: Loop over waiting for the global condition until
the global value matches the wait-for signal.
By default, all sync points are inactive. They do nothing (except to
burn a couple of CPU cycles for checking if they are active).
A sync point becomes active when an action is requested for it.
To do so, put a line like this in the test case file:
SET DEBUG_SYNC= 'after_open_tables SIGNAL opened WAIT_FOR flushed';
This activates the sync point 'after_open_tables'. It requests it to
emit the signal 'opened' and wait for another thread to emit the signal
'flushed' when the thread's execution runs through the sync point.
For every sync point there can be one action per thread only. Every
thread can request multiple actions, but only one per sync point. In
other words, a thread can activate multiple sync points.
Here is an example how to activate and use the sync points:
--connection conn1
SET DEBUG_SYNC= 'after_open_tables SIGNAL opened WAIT_FOR flushed';
send INSERT INTO t1 VALUES(1);
--connection conn2
SET DEBUG_SYNC= 'now WAIT_FOR opened';
SET DEBUG_SYNC= 'after_abort_locks SIGNAL flushed';
FLUSH TABLE t1;
When conn1 runs through the INSERT statement, it hits the sync point
'after_open_tables'. It notices that it is active and executes its
action. It emits the signal 'opened' and waits for another thread to
emit the signal 'flushed'.
conn2 waits immediately at the special sync point 'now' for another
thread to emit the 'opened' signal.
A signal remains in effect until it is overwritten. If conn1 signals
'opened' before conn2 reaches 'now', conn2 will still find the 'opened'
signal. It does not wait in this case.
When conn2 reaches 'after_abort_locks', it signals 'flushed', which lets
conn1 awake.
Normally the activation of a sync point is cleared when it has been
executed. Sometimes it is necessary to keep the sync point active for
another execution. You can add an execute count to the action:
SET DEBUG_SYNC= 'name SIGNAL sig EXECUTE 3';
This sets the signal point's activation counter to 3. Each execution
decrements the counter. After the third execution the sync point
becomes inactive.
One of the primary goals of this facility is to eliminate sleeps from
the test suite. In most cases it should be possible to rewrite test
cases so that they do not need to sleep. (But this facility cannot
synchronize multiple processes.) However, to support test development,
and as a last resort, sync point waiting times out. There is a default
timeout, but it can be overridden:
SET DEBUG_SYNC= 'name WAIT_FOR sig TIMEOUT 10 EXECUTE 2';
TIMEOUT 0 is special: If the signal is not present, the wait times out
immediately.
When a wait timed out (even on TIMEOUT 0), a warning is generated so
that it shows up in the test result.
You can throw an error message and kill the query when a synchronization
point is hit a certain number of times:
SET DEBUG_SYNC= 'name HIT_LIMIT 3';
Or combine it with signal and/or wait:
SET DEBUG_SYNC= 'name SIGNAL sig EXECUTE 2 HIT_LIMIT 3';
Here the first two hits emit the signal, the third hit returns the error
message and kills the query.
For cases where you are not sure that an action is taken and thus
cleared in any case, you can force to clear (deactivate) a sync point:
SET DEBUG_SYNC= 'name CLEAR';
If you want to clear all actions and clear the global signal, use:
SET DEBUG_SYNC= 'RESET';
This is the only way to reset the global signal to an empty string.
For testing of the facility itself you can execute a sync point just
as if it had been hit:
SET DEBUG_SYNC= 'name TEST';
=== Formal Syntax ===
The string to "assign" to the DEBUG_SYNC variable can contain:
{RESET |
<sync point name> TEST |
<sync point name> CLEAR |
<sync point name> {{SIGNAL <signal name> |
WAIT_FOR <signal name> [TIMEOUT <seconds>]}
[EXECUTE <count>] &| HIT_LIMIT <count>}
Here '&|' means 'and/or'. This means that one of the sections
separated by '&|' must be present or both of them.
=== Activation/Deactivation ===
The facility is an optional part of the MySQL server.
It is enabled in a debug server by default.
./configure --enable-debug-sync
The Debug Sync Facility, when compiled in, is disabled by default. It
can be enabled by a mysqld command line option:
--debug-sync-timeout[=default_wait_timeout_value_in_seconds]
'default_wait_timeout_value_in_seconds' is the default timeout for the
WAIT_FOR action. If set to zero, the facility stays disabled.
The facility is enabled by default in the test suite, but can be
disabled with:
mysql-test-run.pl ... --debug-sync-timeout=0 ...
Likewise the default wait timeout can be set:
mysql-test-run.pl ... --debug-sync-timeout=10 ...
The command line option influences the readable value of the system
variable 'debug_sync'.
* If the facility is not compiled in, the system variable does not exist.
* If --debug-sync-timeout=0 the value of the variable reads as "OFF".
* Otherwise the value reads as "ON - current signal: " followed by the
current signal string, which can be empty.
The readable variable value is the same, regardless if read as global
or session value.
Setting the 'debug-sync' system variable requires 'SUPER' privilege.
You can never read back the string that you assigned to the variable,
unless you assign the value that the variable does already have. But
that would give a parse error. A syntactically correct string is
parsed into a debug sync action and stored apart from the variable value.
=== Implementation ===
Pseudo code for a sync point:
#define DEBUG_SYNC(thd, sync_point_name)
if (unlikely(opt_debug_sync_timeout))
debug_sync(thd, STRING_WITH_LEN(sync_point_name))
The sync point performs a binary search in a sorted array of actions
for this thread.
The SET DEBUG_SYNC statement adds a requested action to the array or
overwrites an existing action for the same sync point. When it adds a
new action, the array is sorted again.
=== A typical synchronization pattern ===
There are quite a few places in MySQL, where we use a synchronization
pattern like this:
mysql_mutex_lock(&mutex);
thd->enter_cond(&condition_variable, &mutex, new_message);
#if defined(ENABLE_DEBUG_SYNC)
if (!thd->killed && !end_of_wait_condition)
DEBUG_SYNC(thd, "sync_point_name");
#endif
while (!thd->killed && !end_of_wait_condition)
mysql_cond_wait(&condition_variable, &mutex);
thd->exit_cond(old_message);
Here some explanations:
thd->enter_cond() is used to register the condition variable and the
mutex in thd->mysys_var. This is done to allow the thread to be
interrupted (killed) from its sleep. Another thread can find the
condition variable to signal and mutex to use for synchronization in
this thread's THD::mysys_var.
thd->enter_cond() requires the mutex to be acquired in advance.
thd->exit_cond() unregisters the condition variable and mutex and
releases the mutex.
If you want to have a Debug Sync point with the wait, please place it
behind enter_cond(). Only then you can safely decide, if the wait will
be taken. Also you will have THD::proc_info correct when the sync
point emits a signal. DEBUG_SYNC sets its own proc_info, but restores
the previous one before releasing its internal mutex. As soon as
another thread sees the signal, it does also see the proc_info from
before entering the sync point. In this case it will be "new_message",
which is associated with the wait that is to be synchronized.
In the example above, the wait condition is repeated before the sync
point. This is done to skip the sync point, if no wait takes place.
The sync point is before the loop (not inside the loop) to have it hit
once only. It is possible that the condition variable is signaled
multiple times without the wait condition to be true.
A bit off-topic: At some places, the loop is taken around the whole
synchronization pattern:
while (!thd->killed && !end_of_wait_condition)
{
mysql_mutex_lock(&mutex);
thd->enter_cond(&condition_variable, &mutex, new_message);
if (!thd->killed [&& !end_of_wait_condition])
{
[DEBUG_SYNC(thd, "sync_point_name");]
mysql_cond_wait(&condition_variable, &mutex);
}
thd->exit_cond(old_message);
}
Note that it is important to repeat the test for thd->killed after
enter_cond(). Otherwise the killing thread may kill this thread after
it tested thd->killed in the loop condition and before it registered
the condition variable and mutex in enter_cond(). In this case, the
killing thread does not know that this thread is going to wait on a
condition variable. It would just set THD::killed. But if we would not
test it again, we would go asleep though we are killed. If the killing
thread would kill us when we are after the second test, but still
before sleeping, we hold the mutex, which is registered in mysys_var.
The killing thread would try to acquire the mutex before signaling
the condition variable. Since the mutex is only released implicitly in
mysql_cond_wait(), the signaling happens at the right place. We
have a safe synchronization.
=== Co-work with the DBUG facility ===
When running the MySQL test suite with the --debug command line
option, the Debug Sync Facility writes trace messages to the DBUG
trace. The following shell commands proved very useful in extracting
relevant information:
egrep 'query:|debug_sync_exec:' mysql-test/var/log/mysqld.1.trace
It shows all executed SQL statements and all actions executed by
synchronization points.
Sometimes it is also useful to see, which synchronization points have
been run through (hit) with or without executing actions. Then add
"|debug_sync_point:" to the egrep pattern.
=== Further reading ===
For a discussion of other methods to synchronize threads see
http://forge.mysql.com/wiki/MySQL_Internals_Test_Synchronization
For complete syntax tests, functional tests, and examples see the test
case debug_sync.test.
See also worklog entry WL#4259 - Test Synchronization Facility
*/
#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"
/*
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 */
};
/**
Definitions for the debug sync facility.
1. Global string variable to hold a "signal" ("signal post", "flag mast").
2. Global condition variable for signaling and waiting.
3. Global mutex to synchronize access to the above.
*/
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 */
/**
Callback pointer for C files.
*/
extern "C" void (*debug_sync_C_callback_ptr)(const char *, size_t);
/**
Callbacks from C files.
*/
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
/**
Callback for debug sync, to be used by C files. See thr_lock.c for example.
@description
We cannot place a sync point directly in C files (like those in mysys or
certain storage engines written mostly in C like MyISAM or Maria). Because
they are C code and do not include sql_priv.h. So they do not know the
macro DEBUG_SYNC(thd, sync_point_name). The macro needs a 'thd' argument.
Hence it cannot be used in files outside of the sql/ directory.
The workaround is to call back simple functions like this one from
non-sql/ files.
We want to allow modules like thr_lock to be used without sql/ and
especially without Debug Sync. So we cannot just do a simple call
of the callback function. Instead we provide a global pointer in
the other file, which is to be set to the callback by Debug Sync.
If the pointer is not set, no call back will be done. If Debug
Sync sets the pointer to a callback function like this one, it will
be called. That way thr_lock.c does not have an undefined reference
to Debug Sync and can be used without it. Debug Sync, in contrast,
has an undefined reference to that pointer and thus requires
thr_lock to be linked too. But this is not a problem as it is part
of the MySQL server anyway.
@note
The callback pointer in C files is set only if debug sync is
initialized. And this is done only if opt_debug_sync_timeout is set.
*/
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;
if (PSI_server == NULL)
return;
count= array_elements(all_debug_sync_mutexes);
PSI_server->register_mutex(category, all_debug_sync_mutexes, count);
count= array_elements(all_debug_sync_conds);
PSI_server->register_cond(category, all_debug_sync_conds, count);
}
#endif /* HAVE_PSI_INTERFACE */
/**
Initialize the debug sync facility at server start.
@return status
@retval 0 ok
@retval != 0 error
*/
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);
}
/**
End the debug sync facility.
@description
This is called at server shutdown or after a thread initialization error.
*/
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 */
/**
Disable the facility after lack of memory if no error can be returned.
@note
Do not end the facility here because the global variables can
be in use by other threads.
*/
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 */
/**
Initialize the debug sync facility at thread start.
@param[in] thd thread handle
*/
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;
}
/**
End the debug sync facility at thread end.
@param[in] thd thread handle
*/
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;
}
/**
Move a string by length.
@param[out] to buffer for the resulting string
@param[in] to_end end of buffer
@param[in] from source string
@param[in] length number of bytes to copy
@return pointer to end of copied string
*/
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)
/**
Create a string that describes an action.
@param[out] result buffer for the resulting string
@param[in] size size of result buffer
@param[in] action action to describe
*/
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';
}
/**
Print actions.
@param[in] thd thread handle
*/
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) */
/**
Compare two actions by sync point name length, string.
@param[in] arg1 reference to action1
@param[in] arg2 reference to action2
@return difference
@retval == 0 length1/string1 is same as length2/string2
@retval < 0 length1/string1 is smaller
@retval > 0 length1/string1 is bigger
*/
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;
}
/**
Find a debug sync action.
@param[in] actionarr array of debug sync actions
@param[in] quantity number of actions in array
@param[in] dsp_name name of debug sync point to find
@param[in] name_len length of name of debug sync point
@return action
@retval != NULL found sync point in array
@retval NULL not found
@description
Binary search. Array needs to be sorted by length, sync point name.
*/
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;
}
/**
Reset the debug sync facility.
@param[in] thd thread handle
@description
Remove all actions of this thread.
Clear the global signal.
*/
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;
}
/**
Remove a debug sync action.
@param[in] ds_control control object
@param[in] action action to be removed
@description
Removing an action mainly means to decrement the ds_active counter.
But if the action is between other active action in the array, then
the array needs to be shrinked. The active actions above the one to
be removed have to be moved down by one slot.
*/
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;
}
/**
Get a debug sync action.
@param[in] thd thread handle
@param[in] dsp_name debug sync point name
@param[in] name_len length of sync point name
@return action
@retval != NULL ok
@retval NULL error
@description
Find the debug sync action for a debug sync point or make a new one.
*/
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. */
bzero((uchar*) (ds_control->ds_action + dsp_idx),
(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 */
}
/**
Set a debug sync action.
@param[in] thd thread handle
@param[in] action synchronization action
@return status
@retval FALSE ok
@retval TRUE error
@description
This is called from the debug sync parser. It arms the action for
the requested sync point. If the action parsed into an empty action,
it is removed instead.
Setting an action for a sync point means to make the sync point
active. When it is hit it will execute this action.
Before parsing, we "get" an action object. This is placed at the
end of the thread's action array unless the requested sync point
has an action already.
Then the parser fills the action object from the request string.
Finally the action is "set" for the sync point. If it was parsed
to be empty, it is removed from the array. If it did belong to a
sync point before, the sync point becomes inactive. If the action
became non-empty and it did not belong to a sync point before (it
was added at the end of the action array), the action array needs
to be sorted by sync point.
If the sync point name is "now", it is executed immediately.
*/
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);
}
/**
Extract a token from a string.
@param[out] token_p returns start of token
@param[out] token_length_p returns length of token
@param[in,out] ptr current string pointer, adds '\0' terminators
@return string pointer or NULL
@retval != NULL ptr behind token terminator or at string end
@retval NULL no token found in remainder of string
@note
This function assumes that the string is in system_charset_info,
that this charset is single byte for ASCII NUL ('\0'), that no
character except of ASCII NUL ('\0') contains a byte with value 0,
and that ASCII NUL ('\0') is used as the string terminator.
This function needs to return tokens that are terminated with ASCII
NUL ('\0'). The tokens are used in my_strcasecmp(). Unfortunately
there is no my_strncasecmp().
To return the last token without copying it, we require the input
string to be nul terminated.
@description
This function skips space characters at string begin.
It returns a pointer to the first non-space character in *token_p.
If no non-space character is found before the string terminator
ASCII NUL ('\0'), the function returns NULL. *token_p and
*token_length_p remain unchanged in this case (they are not set).
The function takes a space character or an ASCII NUL ('\0') as a
terminator of the token. The space character could be multi-byte.
It returns the length of the token in bytes, excluding the
terminator, in *token_length_p.
If the terminator of the token is ASCII NUL ('\0'), it returns a
pointer to the terminator (string end).
If the terminator is a space character, it replaces the the first
byte of the terminator character by ASCII NUL ('\0'), skips the (now
corrupted) terminator character, and skips all following space
characters. It returns a pointer to the next non-space character or
to the string terminator ASCII NUL ('\0').
*/
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;
}
/**
Extract a number from a string.
@param[out] number_p returns number
@param[in] actstrptr current pointer in action string
@return string pointer or NULL
@retval != NULL ptr behind token terminator or at string end
@retval NULL no token found or token is not valid number
@note
The same assumptions about charset apply as for debug_sync_token().
@description
This function fetches a token from the string and converts it
into a number.
If there is no token left in the string, or the token is not a valid
decimal number, NULL is returned. The result in *number_p is
undefined in this case.
*/
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;
}
/**
Evaluate a debug sync action string.
@param[in] thd thread handle
@param[in,out] action_str action string to receive '\0' terminators
@return status
@retval FALSE ok
@retval TRUE error
@description
This is called when the DEBUG_SYNC system variable is set.
Parse action string, build a debug sync action, activate it.
Before parsing, we "get" an action object. This is placed at the
end of the thread's action array unless the requested sync point
has an action already.
Then the parser fills the action object from the request string.
Finally the action is "set" for the sync point. This means that the
sync point becomes active or inactive, depending on the action
values.
@note
The input string needs to be ASCII NUL ('\0') terminated. We split
nul-terminated tokens in it without copy.
@see the function comment of debug_sync_token() for more constraints
for the string.
*/
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 bzero(). 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);
}
/**
Set the system variable 'debug_sync'.
@param[in] thd thread handle
@param[in] var set variable request
@return status
@retval FALSE ok, variable is set
@retval TRUE error, variable could not be set
@note
"Setting" of the system variable 'debug_sync' does not mean to
assign a value to it as usual. Instead a debug sync action is parsed
from the input string and stored apart from the variable value.
@note
For efficiency reasons, the action string parser places '\0'
terminators in the string. So we need to take a copy here.
*/
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);
}
/**
Retrieve the value of the system variable 'debug_sync'.
@param[in] thd thread handle
@return string
@retval != NULL ok, string pointer
@retval NULL memory allocation error
@note
The value of the system variable 'debug_sync' reflects if
the facility is enabled ("ON") or disabled (default, "OFF").
When "ON", the current signal is added.
*/
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);
}
/**
Execute requested action at a synchronization point.
@param[in] thd thread handle
@param[in] action action to be executed
@note
This is to be called only if activation count > 0.
*/
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 *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;
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().
*/
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;
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)
{
push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
ER_DEBUG_SYNC_TIMEOUT, ER(ER_DEBUG_SYNC_TIMEOUT));
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);
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
{
/* 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;
}
/**
Execute requested action at a synchronization point.
@param[in] thd thread handle
@param[in] sync_point_name name of synchronization point
@param[in] name_len length of sync point name
*/
void debug_sync(THD *thd, const char *sync_point_name, size_t name_len)
{
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;
}
/**
Define debug sync action.
@param[in] thd thread handle
@param[in] action_str action string
@return status
@retval FALSE ok
@retval TRUE error
@description
The function is similar to @c debug_sync_eval_action but is
to be called immediately from the server code rather than
to be triggered by setting a value to DEBUG_SYNC system variable.
@note
The input string is copied prior to be fed to
@c debug_sync_eval_action to let the latter modify it.
Caution.
The function allocates in THD::mem_root and therefore
is not recommended to be deployed inside big loops.
*/
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) */
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