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Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled

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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.
This commit is contained in:
Davi Arnaut
2010-07-08 18:20:08 -03:00
parent d3b01fef18
commit f56dd32bf7
217 changed files with 1012 additions and 1821 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
sql/sql_plugin.cc
View File

@@ -254,10 +254,9 @@ static void plugin_vars_free_values(sys_var *vars);
static void restore_pluginvar_names(sys_var *first);
static void plugin_opt_set_limits(struct my_option *,
const struct st_mysql_sys_var *);
#define my_intern_plugin_lock(A,B) intern_plugin_lock(A,B CALLER_INFO)
#define my_intern_plugin_lock_ci(A,B) intern_plugin_lock(A,B ORIG_CALLER_INFO)
static plugin_ref intern_plugin_lock(LEX *lex, plugin_ref plugin
CALLER_INFO_PROTO);
#define my_intern_plugin_lock(A,B) intern_plugin_lock(A,B)
#define my_intern_plugin_lock_ci(A,B) intern_plugin_lock(A,B)
static plugin_ref intern_plugin_lock(LEX *lex, plugin_ref plugin);
static void intern_plugin_unlock(LEX *lex, plugin_ref plugin);
static void reap_plugins(void);
@@ -392,9 +391,9 @@ static inline void free_plugin_mem(struct st_plugin_dl *p)
if (p->handle)
dlclose(p->handle);
#endif
my_free(p->dl.str, MYF(MY_ALLOW_ZERO_PTR));
my_free(p->dl.str);
if (p->version != MYSQL_PLUGIN_INTERFACE_VERSION)
my_free((uchar*)p->plugins, MYF(MY_ALLOW_ZERO_PTR));
my_free(p->plugins);
}
@@ -660,7 +659,7 @@ SHOW_COMP_OPTION plugin_status(const char *name, int len, size_t type)
}
static plugin_ref intern_plugin_lock(LEX *lex, plugin_ref rc CALLER_INFO_PROTO)
static plugin_ref intern_plugin_lock(LEX *lex, plugin_ref rc)
{
st_plugin_int *pi= plugin_ref_to_int(rc);
DBUG_ENTER("intern_plugin_lock");
@@ -682,7 +681,7 @@ static plugin_ref intern_plugin_lock(LEX *lex, plugin_ref rc CALLER_INFO_PROTO)
memory manager and/or valgrind to track locked references and
double unlocks to aid resolving reference counting problems.
*/
if (!(plugin= (plugin_ref) my_malloc_ci(sizeof(pi), MYF(MY_WME))))
if (!(plugin= (plugin_ref) my_malloc(sizeof(pi), MYF(MY_WME))))
DBUG_RETURN(NULL);
*plugin= pi;
@@ -699,7 +698,7 @@ static plugin_ref intern_plugin_lock(LEX *lex, plugin_ref rc CALLER_INFO_PROTO)
}
plugin_ref plugin_lock(THD *thd, plugin_ref *ptr CALLER_INFO_PROTO)
plugin_ref plugin_lock(THD *thd, plugin_ref *ptr)
{
LEX *lex= thd ? thd->lex : 0;
plugin_ref rc;
@@ -711,8 +710,7 @@ plugin_ref plugin_lock(THD *thd, plugin_ref *ptr CALLER_INFO_PROTO)
}
plugin_ref plugin_lock_by_name(THD *thd, const LEX_STRING *name, int type
CALLER_INFO_PROTO)
plugin_ref plugin_lock_by_name(THD *thd, const LEX_STRING *name, int type)
{
LEX *lex= thd ? thd->lex : 0;
plugin_ref rc= NULL;
@@ -973,7 +971,7 @@ static void intern_plugin_unlock(LEX *lex, plugin_ref plugin)
if (!pi->plugin_dl)
DBUG_VOID_RETURN;
#else
my_free((uchar*) plugin, MYF(MY_WME));
my_free(plugin);
#endif
DBUG_PRINT("info",("unlocking plugin, name= %s, ref_count= %d",
@@ -2245,7 +2243,7 @@ static void update_func_str(THD *thd, struct st_mysql_sys_var *var,
if (var->flags & PLUGIN_VAR_MEMALLOC)
{
*(char **)tgt= my_strdup(*(char **) save, MYF(0));
my_free(old, MYF(0));
my_free(old);
}
}
@@ -2637,7 +2635,7 @@ static void cleanup_variables(THD *thd, struct system_variables *vars)
flags & PLUGIN_VAR_THDLOCAL && flags & PLUGIN_VAR_MEMALLOC)
{
char **ptr= (char**) pivar->real_value_ptr(thd, OPT_SESSION);
my_free(*ptr, MYF(MY_WME | MY_FAE | MY_ALLOW_ZERO_PTR));
my_free(*ptr);
*ptr= NULL;
}
}
@@ -2645,7 +2643,7 @@ static void cleanup_variables(THD *thd, struct system_variables *vars)
DBUG_ASSERT(vars->table_plugin == NULL);
my_free(vars->dynamic_variables_ptr, MYF(MY_ALLOW_ZERO_PTR));
my_free(vars->dynamic_variables_ptr);
vars->dynamic_variables_ptr= NULL;
vars->dynamic_variables_size= 0;
vars->dynamic_variables_version= 0;
@@ -2706,7 +2704,7 @@ static void plugin_vars_free_values(sys_var *vars)
char **valptr= (char**) piv->real_value_ptr(NULL, OPT_GLOBAL);
DBUG_PRINT("plugin", ("freeing value for: '%s' addr: 0x%lx",
var->name.str, (long) valptr));
my_free(*valptr, MYF(MY_WME | MY_FAE | MY_ALLOW_ZERO_PTR));
my_free(*valptr);
*valptr= NULL;
}
}