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MDEV-10010 - potential deadlock on windows due to recursive

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SRWLock acquisition

Backport patch from 10.1
This commit is contained in:
Vladislav Vaintroub
2016-08-03 13:42:46 +00:00
parent 141f88d1d5
commit 511313b9d6
3 changed files with 82 additions and 65 deletions
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126
sql/sql_plugin.cc
View File

@ -2896,68 +2896,8 @@ static uchar *intern_sys_var_ptr(THD* thd, int offset, bool global_lock)
if (!thd->variables.dynamic_variables_ptr || if (!thd->variables.dynamic_variables_ptr ||
(uint)offset > thd->variables.dynamic_variables_head) (uint)offset > thd->variables.dynamic_variables_head)
{ {
uint idx;
mysql_rwlock_rdlock(&LOCK_system_variables_hash); mysql_rwlock_rdlock(&LOCK_system_variables_hash);
sync_dynamic_session_variables(thd, global_lock);
thd->variables.dynamic_variables_ptr= (char*)
my_realloc(thd->variables.dynamic_variables_ptr,
global_variables_dynamic_size,
MYF(MY_WME | MY_FAE | MY_ALLOW_ZERO_PTR));
if (global_lock)
mysql_mutex_lock(&LOCK_global_system_variables);
mysql_mutex_assert_owner(&LOCK_global_system_variables);
memcpy(thd->variables.dynamic_variables_ptr +
thd->variables.dynamic_variables_size,
global_system_variables.dynamic_variables_ptr +
thd->variables.dynamic_variables_size,
global_system_variables.dynamic_variables_size -
thd->variables.dynamic_variables_size);
/*
now we need to iterate through any newly copied 'defaults'
and if it is a string type with MEMALLOC flag, we need to strdup
*/
for (idx= 0; idx < bookmark_hash.records; idx++)
{
sys_var_pluginvar *pi;
sys_var *var;
st_bookmark *v= (st_bookmark*) my_hash_element(&bookmark_hash,idx);
if (v->version <= thd->variables.dynamic_variables_version)
continue; /* already in thd->variables */
if (!(var= intern_find_sys_var(v->key + 1, v->name_len)) ||
!(pi= var->cast_pluginvar()) ||
v->key[0] != plugin_var_bookmark_key(pi->plugin_var->flags))
continue;
/* Here we do anything special that may be required of the data types */
if ((pi->plugin_var->flags & PLUGIN_VAR_TYPEMASK) == PLUGIN_VAR_STR &&
pi->plugin_var->flags & PLUGIN_VAR_MEMALLOC)
{
char **pp= (char**) (thd->variables.dynamic_variables_ptr +
*(int*)(pi->plugin_var + 1));
if ((*pp= *(char**) (global_system_variables.dynamic_variables_ptr +
*(int*)(pi->plugin_var + 1))))
*pp= my_strdup(*pp, MYF(MY_WME|MY_FAE));
}
}
if (global_lock)
mysql_mutex_unlock(&LOCK_global_system_variables);
thd->variables.dynamic_variables_version=
global_system_variables.dynamic_variables_version;
thd->variables.dynamic_variables_head=
global_system_variables.dynamic_variables_head;
thd->variables.dynamic_variables_size=
global_system_variables.dynamic_variables_size;
mysql_rwlock_unlock(&LOCK_system_variables_hash); mysql_rwlock_unlock(&LOCK_system_variables_hash);
} }
DBUG_RETURN((uchar*)thd->variables.dynamic_variables_ptr + offset); DBUG_RETURN((uchar*)thd->variables.dynamic_variables_ptr + offset);
@ -3037,6 +2977,70 @@ void plugin_thdvar_init(THD *thd)
} }
void sync_dynamic_session_variables(THD* thd, bool global_lock)
{
uint idx;
thd->variables.dynamic_variables_ptr= (char*)
my_realloc(thd->variables.dynamic_variables_ptr,
global_variables_dynamic_size,
MYF(MY_WME | MY_FAE | MY_ALLOW_ZERO_PTR));
if (global_lock)
mysql_mutex_lock(&LOCK_global_system_variables);
mysql_mutex_assert_owner(&LOCK_global_system_variables);
memcpy(thd->variables.dynamic_variables_ptr +
thd->variables.dynamic_variables_size,
global_system_variables.dynamic_variables_ptr +
thd->variables.dynamic_variables_size,
global_system_variables.dynamic_variables_size -
thd->variables.dynamic_variables_size);
/*
now we need to iterate through any newly copied 'defaults'
and if it is a string type with MEMALLOC flag, we need to strdup
*/
for (idx= 0; idx < bookmark_hash.records; idx++)
{
sys_var_pluginvar *pi;
sys_var *var;
st_bookmark *v= (st_bookmark*) my_hash_element(&bookmark_hash,idx);
if (v->version <= thd->variables.dynamic_variables_version)
continue; /* already in thd->variables */
if (!(var= intern_find_sys_var(v->key + 1, v->name_len)) ||
!(pi= var->cast_pluginvar()) ||
v->key[0] != plugin_var_bookmark_key(pi->plugin_var->flags))
continue;
/* Here we do anything special that may be required of the data types */
if ((pi->plugin_var->flags & PLUGIN_VAR_TYPEMASK) == PLUGIN_VAR_STR &&
pi->plugin_var->flags & PLUGIN_VAR_MEMALLOC)
{
int offset= ((thdvar_str_t *)(pi->plugin_var))->offset;
char **pp= (char**) (thd->variables.dynamic_variables_ptr + offset);
if (*pp)
*pp= my_strdup(*pp, MYF(MY_WME|MY_FAE));
}
}
if (global_lock)
mysql_mutex_unlock(&LOCK_global_system_variables);
thd->variables.dynamic_variables_version=
global_system_variables.dynamic_variables_version;
thd->variables.dynamic_variables_head=
global_system_variables.dynamic_variables_head;
thd->variables.dynamic_variables_size=
global_system_variables.dynamic_variables_size;
}
/* /*
Unlocks all system variables which hold a reference Unlocks all system variables which hold a reference
*/ */

2
sql/sql_plugin.h
View File

@ -174,4 +174,6 @@ typedef my_bool (plugin_foreach_func)(THD *thd,
#define plugin_foreach(A,B,C,D) plugin_foreach_with_mask(A,B,C,PLUGIN_IS_READY,D) #define plugin_foreach(A,B,C,D) plugin_foreach_with_mask(A,B,C,PLUGIN_IS_READY,D)
extern bool plugin_foreach_with_mask(THD *thd, plugin_foreach_func *func, extern bool plugin_foreach_with_mask(THD *thd, plugin_foreach_func *func,
int type, uint state_mask, void *arg); int type, uint state_mask, void *arg);
extern void sync_dynamic_session_variables(THD* thd, bool global_lock);
#endif #endif

19
sql/sql_show.cc
View File

@ -6937,19 +6937,30 @@ int fill_variables(THD *thd, TABLE_LIST *tables, COND *cond)
const char *wild= lex->wild ? lex->wild->ptr() : NullS; const char *wild= lex->wild ? lex->wild->ptr() : NullS;
enum enum_schema_tables schema_table_idx= enum enum_schema_tables schema_table_idx=
get_schema_table_idx(tables->schema_table); get_schema_table_idx(tables->schema_table);
enum enum_var_type option_type= OPT_SESSION; enum enum_var_type scope= OPT_SESSION;
bool upper_case_names= (schema_table_idx != SCH_VARIABLES); bool upper_case_names= (schema_table_idx != SCH_VARIABLES);
bool sorted_vars= (schema_table_idx == SCH_VARIABLES); bool sorted_vars= (schema_table_idx == SCH_VARIABLES);
if ((sorted_vars && lex->option_type == OPT_GLOBAL) || if ((sorted_vars && lex->option_type == OPT_GLOBAL) ||
schema_table_idx == SCH_GLOBAL_VARIABLES) schema_table_idx == SCH_GLOBAL_VARIABLES)
option_type= OPT_GLOBAL; scope= OPT_GLOBAL;
COND *partial_cond= make_cond_for_info_schema(cond, tables); COND *partial_cond= make_cond_for_info_schema(cond, tables);
mysql_rwlock_rdlock(&LOCK_system_variables_hash); mysql_rwlock_rdlock(&LOCK_system_variables_hash);
res= show_status_array(thd, wild, enumerate_sys_vars(thd, sorted_vars, option_type),
option_type, NULL, "", tables->table, /*
Avoid recursive LOCK_system_variables_hash acquisition in
intern_sys_var_ptr() by pre-syncing dynamic session variables.
*/
if (scope == OPT_SESSION &&
(!thd->variables.dynamic_variables_ptr ||
global_system_variables.dynamic_variables_head >
thd->variables.dynamic_variables_head))
sync_dynamic_session_variables(thd, true);
res= show_status_array(thd, wild, enumerate_sys_vars(thd, sorted_vars, scope),
scope, NULL, "", tables->table,
upper_case_names, partial_cond); upper_case_names, partial_cond);
mysql_rwlock_unlock(&LOCK_system_variables_hash); mysql_rwlock_unlock(&LOCK_system_variables_hash);
DBUG_RETURN(res); DBUG_RETURN(res);