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Remove non-functional code for unloading loadable modules. 

The code for unloading a library has been commented-out for over 12
years, ever since commit 602a9ef5a7, and we're
no closer to supporting it now than we were back then.

Nathan Bossart, reviewed by Michael Paquier and by me.

Discussion: http://postgr.es/m/Ynsc9bRL1caUSBSE@paquier.xyz
This commit is contained in:
Robert Haas 2022-05-11 15:27:33 -04:00
parent 78ccd6cca4
commit ab02d702ef
13 changed files with 13 additions and 200 deletions
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14
contrib/auto_explain/auto_explain.c
View File

@ -77,7 +77,6 @@ static ExecutorFinish_hook_type prev_ExecutorFinish = NULL;
static ExecutorEnd_hook_type prev_ExecutorEnd = NULL;
void _PG_init(void);
void _PG_fini(void);
static void explain_ExecutorStart(QueryDesc *queryDesc, int eflags);
static void explain_ExecutorRun(QueryDesc *queryDesc,
@ -244,19 +243,6 @@ _PG_init(void)
ExecutorEnd_hook = explain_ExecutorEnd;
}
/*
* Module unload callback
*/
void
_PG_fini(void)
{
/* Uninstall hooks. */
ExecutorStart_hook = prev_ExecutorStart;
ExecutorRun_hook = prev_ExecutorRun;
ExecutorFinish_hook = prev_ExecutorFinish;
ExecutorEnd_hook = prev_ExecutorEnd;
}
/*
* ExecutorStart hook: start up logging if needed
*/

11
contrib/passwordcheck/passwordcheck.c
View File

@ -33,7 +33,6 @@ static check_password_hook_type prev_check_password_hook = NULL;
#define MIN_PWD_LENGTH 8
extern void _PG_init(void);
extern void _PG_fini(void);
/*
* check_password
@ -149,13 +148,3 @@ _PG_init(void)
prev_check_password_hook = check_password_hook;
check_password_hook = check_password;
}
/*
* Module unload function
*/
void
_PG_fini(void)
{
/* uninstall hook */
check_password_hook = prev_check_password_hook;
}

18
contrib/pg_stat_statements/pg_stat_statements.c
View File

@ -305,7 +305,6 @@ static bool pgss_save; /* whether to save stats across shutdown */
/*---- Function declarations ----*/
void _PG_init(void);
void _PG_fini(void);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset_1_7);
@ -481,23 +480,6 @@ _PG_init(void)
ProcessUtility_hook = pgss_ProcessUtility;
}
/*
* Module unload callback
*/
void
_PG_fini(void)
{
/* Uninstall hooks. */
shmem_startup_hook = prev_shmem_startup_hook;
post_parse_analyze_hook = prev_post_parse_analyze_hook;
planner_hook = prev_planner_hook;
ExecutorStart_hook = prev_ExecutorStart;
ExecutorRun_hook = prev_ExecutorRun;
ExecutorFinish_hook = prev_ExecutorFinish;
ExecutorEnd_hook = prev_ExecutorEnd;
ProcessUtility_hook = prev_ProcessUtility;
}
/*
* shmem_startup hook: allocate or attach to shared memory,
* then load any pre-existing statistics from file.

18
doc/src/sgml/xfunc.sgml
View File

@ -1978,28 +1978,16 @@ PG_MODULE_MAGIC;
<indexterm zone="xfunc-c-dynload">
<primary>_PG_init</primary>
</indexterm>
<indexterm zone="xfunc-c-dynload">
<primary>_PG_fini</primary>
</indexterm>
<indexterm zone="xfunc-c-dynload">
<primary>library initialization function</primary>
</indexterm>
<indexterm zone="xfunc-c-dynload">
<primary>library finalization function</primary>
</indexterm>
<para>
Optionally, a dynamically loaded file can contain initialization and
finalization functions. If the file includes a function named
Optionally, a dynamically loaded file can contain an initialization
function. If the file includes a function named
<function>_PG_init</function>, that function will be called immediately after
loading the file. The function receives no parameters and should
return void. If the file includes a function named
<function>_PG_fini</function>, that function will be called immediately before
unloading the file. Likewise, the function receives no parameters and
should return void. Note that <function>_PG_fini</function> will only be called
during an unload of the file, not during process termination.
(Presently, unloads are disabled and will never occur, but this may
change in the future.)
return void. There is presently no way to unload a dynamically loaded file.
</para>
</sect2>

2
src/backend/postmaster/pgarch.c
View File

@ -802,7 +802,7 @@ HandlePgArchInterrupts(void)
* Ideally, we would simply unload the previous archive module and
* load the new one, but there is presently no mechanism for
* unloading a library (see the comment above
* internal_unload_library()). To deal with this, we simply restart
* internal_load_library()). To deal with this, we simply restart
* the archiver. The new archive module will be loaded when the new
* archiver process starts up.
*/

77
src/backend/utils/fmgr/dfmgr.c
View File

@ -37,9 +37,8 @@
#include "utils/hsearch.h"
/* signatures for PostgreSQL-specific library init/fini functions */
/* signature for PostgreSQL-specific library init function */
typedef void (*PG_init_t) (void);
typedef void (*PG_fini_t) (void);
/* hashtable entry for rendezvous variables */
typedef struct
@ -79,7 +78,6 @@ char *Dynamic_library_path;
static void *internal_load_library(const char *libname);
static void incompatible_module_error(const char *libname,
const Pg_magic_struct *module_magic_data) pg_attribute_noreturn();
static void internal_unload_library(const char *libname);
static bool file_exists(const char *name);
static char *expand_dynamic_library_name(const char *name);
static void check_restricted_library_name(const char *name);
@ -154,9 +152,6 @@ load_file(const char *filename, bool restricted)
/* Expand the possibly-abbreviated filename to an exact path name */
fullname = expand_dynamic_library_name(filename);
/* Unload the library if currently loaded */
internal_unload_library(fullname);
/* Load the shared library */
(void) internal_load_library(fullname);
@ -179,6 +174,11 @@ lookup_external_function(void *filehandle, const char *funcname)
* loaded. Return the pg_dl* handle for the file.
*
* Note: libname is expected to be an exact name for the library file.
*
* NB: There is presently no way to unload a dynamically loaded file. We might
* add one someday if we can convince ourselves we have safe protocols for un-
* hooking from hook function pointers, releasing custom GUC variables, and
* perhaps other things that are definitely unsafe currently.
*/
static void *
internal_load_library(const char *libname)
@ -400,71 +400,6 @@ incompatible_module_error(const char *libname,
errdetail_internal("%s", details.data)));
}
/*
* Unload the specified dynamic-link library file, if it is loaded.
*
* Note: libname is expected to be an exact name for the library file.
*
* XXX for the moment, this is disabled, resulting in LOAD of an already-loaded
* library always being a no-op. We might re-enable it someday if we can
* convince ourselves we have safe protocols for un-hooking from hook function
* pointers, releasing custom GUC variables, and perhaps other things that
* are definitely unsafe currently.
*/
static void
internal_unload_library(const char *libname)
{
#ifdef NOT_USED
DynamicFileList *file_scanner,
*prv,
*nxt;
struct stat stat_buf;
PG_fini_t PG_fini;
/*
* We need to do stat() in order to determine whether this is the same
* file as a previously loaded file; it's also handy so as to give a good
* error message if bogus file name given.
*/
if (stat(libname, &stat_buf) == -1)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not access file \"%s\": %m", libname)));
/*
* We have to zap all entries in the list that match on either filename or
* inode, else internal_load_library() will still think it's present.
*/
prv = NULL;
for (file_scanner = file_list; file_scanner != NULL; file_scanner = nxt)
{
nxt = file_scanner->next;
if (strcmp(libname, file_scanner->filename) == 0 ||
SAME_INODE(stat_buf, *file_scanner))
{
if (prv)
prv->next = nxt;
else
file_list = nxt;
/*
* If the library has a _PG_fini() function, call it.
*/
PG_fini = (PG_fini_t) dlsym(file_scanner->handle, "_PG_fini");
if (PG_fini)
(*PG_fini) ();
clear_external_function_hash(file_scanner->handle);
dlclose(file_scanner->handle);
free((char *) file_scanner);
/* prv does not change */
}
else
prv = file_scanner;
}
#endif /* NOT_USED */
}
static bool
file_exists(const char *name)
{

14
src/backend/utils/fmgr/fmgr.c
View File

@ -582,20 +582,6 @@ record_C_func(HeapTuple procedureTuple,
entry->inforec = inforec;
}
/*
* clear_external_function_hash: remove entries for a library being closed
*
* Presently we just zap the entire hash table, but later it might be worth
* the effort to remove only the entries associated with the given handle.
*/
void
clear_external_function_hash(void *filehandle)
{
if (CFuncHash)
hash_destroy(CFuncHash);
CFuncHash = NULL;
}
/*
* Copy an FmgrInfo struct

1
src/include/fmgr.h
View File

@ -705,7 +705,6 @@ extern bytea *OidSendFunctionCall(Oid functionId, Datum val);
* Routines in fmgr.c
*/
extern const Pg_finfo_record *fetch_finfo_record(void *filehandle, const char *funcname);
extern void clear_external_function_hash(void *filehandle);
extern Oid fmgr_internal_function(const char *proname);
extern Oid get_fn_expr_rettype(FmgrInfo *flinfo);
extern Oid get_fn_expr_argtype(FmgrInfo *flinfo, int argnum);

2
src/pl/plpgsql/src/plpgsql.h
View File

@ -1100,8 +1100,6 @@ typedef struct PLpgSQL_execstate
* variable "PLpgSQL_plugin" and set it to point to a PLpgSQL_plugin struct.
* Typically the struct could just be static data in the plugin library.
* We expect that a plugin would do this at library load time (_PG_init()).
* It must also be careful to set the rendezvous variable back to NULL
* if it is unloaded (_PG_fini()).
*
* This structure is basically a collection of function pointers --- at
* various interesting points in pl_exec.c, we call these functions

10
src/test/modules/delay_execution/delay_execution.c
View File

@ -36,9 +36,8 @@ static int post_planning_lock_id = 0;
/* Save previous planner hook user to be a good citizen */
static planner_hook_type prev_planner_hook = NULL;
/* Module load/unload functions */
/* Module load function */
void _PG_init(void);
void _PG_fini(void);
/* planner_hook function to provide the desired delay */
@ -97,10 +96,3 @@ _PG_init(void)
prev_planner_hook = planner_hook;
planner_hook = delay_execution_planner;
}
/* Module unload function (pro forma, not used currently) */
void
_PG_fini(void)
{
planner_hook = prev_planner_hook;
}

7
src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
View File

@ -21,7 +21,6 @@
PG_MODULE_MAGIC;
void _PG_init(void);
void _PG_fini(void);
static char *ssl_passphrase = NULL;
@ -55,12 +54,6 @@ _PG_init(void)
openssl_tls_init_hook = set_rot13;
}
void
_PG_fini(void)
{
/* do nothing yet */
}
static void
set_rot13(SSL_CTX *context, bool isServerStart)
{

22
src/test/modules/test_oat_hooks/test_oat_hooks.c
View File

@ -43,7 +43,7 @@ static bool REGRESS_userset_variable2 = false;
static bool REGRESS_suset_variable1 = false;
static bool REGRESS_suset_variable2 = false;
/* Saved hook values in case of unload */
/* Saved hook values */
static object_access_hook_type next_object_access_hook = NULL;
static object_access_hook_type_str next_object_access_hook_str = NULL;
static ExecutorCheckPerms_hook_type next_exec_check_perms_hook = NULL;
@ -70,10 +70,9 @@ static char *accesstype_arg_to_string(ObjectAccessType access, void *arg);
void _PG_init(void);
void _PG_fini(void);
/*
* Module load/unload callback
* Module load callback
*/
void
_PG_init(void)
@ -231,23 +230,6 @@ _PG_init(void)
ProcessUtility_hook = REGRESS_utility_command;
}
void
_PG_fini(void)
{
/* Unload hooks */
if (object_access_hook == REGRESS_object_access_hook)
object_access_hook = next_object_access_hook;
if (object_access_hook_str == REGRESS_object_access_hook_str)
object_access_hook_str = next_object_access_hook_str;
if (ExecutorCheckPerms_hook == REGRESS_exec_check_perms)
ExecutorCheckPerms_hook = next_exec_check_perms_hook;
if (ProcessUtility_hook == REGRESS_utility_command)
ProcessUtility_hook = next_ProcessUtility_hook;
}
static void
emit_audit_message(const char *type, const char *hook, char *action, char *objName)
{

17
src/test/modules/test_rls_hooks/test_rls_hooks.c
View File

@ -29,34 +29,17 @@
PG_MODULE_MAGIC;
/* Saved hook values in case of unload */
static row_security_policy_hook_type prev_row_security_policy_hook_permissive = NULL;
static row_security_policy_hook_type prev_row_security_policy_hook_restrictive = NULL;
void _PG_init(void);
void _PG_fini(void);
/* Install hooks */
void
_PG_init(void)
{
/* Save values for unload */
prev_row_security_policy_hook_permissive = row_security_policy_hook_permissive;
prev_row_security_policy_hook_restrictive = row_security_policy_hook_restrictive;
/* Set our hooks */
row_security_policy_hook_permissive = test_rls_hooks_permissive;
row_security_policy_hook_restrictive = test_rls_hooks_restrictive;
}
/* Uninstall hooks */
void
_PG_fini(void)
{
row_security_policy_hook_permissive = prev_row_security_policy_hook_permissive;
row_security_policy_hook_restrictive = prev_row_security_policy_hook_restrictive;
}
/*
* Return permissive policies to be added
*/