[CF 5940] v20 - Improve LWLock tranche name visibility across backends

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5940

The branch will be overwritten each time a new patch version is posted to
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on the master branch.

Patch(es): https://www.postgresql.org/message-id/aLMHVosexT5D-Ybz@nathan
Author(s): Sami Imseih

Author: Commitfest Bot

contrib/pg_prewarm/autoprewarm.c

@@ -864,7 +864,7 @@ apw_init_state(void *ptr)
 {
 	AutoPrewarmSharedState *state = (AutoPrewarmSharedState *) ptr;
 
-	LWLockInitialize(&state->lock, LWLockNewTrancheId());
+	LWLockInitialize(&state->lock, LWLockNewTrancheId("autoprewarm"));
 	state->bgworker_pid = InvalidPid;
 	state->pid_using_dumpfile = InvalidPid;
 }
@@ -883,7 +883,6 @@ apw_init_shmem(void)
 								   sizeof(AutoPrewarmSharedState),
 								   apw_init_state,
 								   &found);
-	LWLockRegisterTranche(apw_state->lock.tranche, "autoprewarm");
 
 	return found;
 }

doc/src/sgml/xfunc.sgml

@@ -3759,7 +3759,7 @@ LWLockPadded *GetNamedLWLockTranche(const char *tranche_name)
       <literal>shmem_request_hook</literal>.  To do so, first allocate a
       <literal>tranche_id</literal> by calling:
 <programlisting>
-int LWLockNewTrancheId(void)
+int LWLockNewTrancheId(const char *name)
 </programlisting>
       Next, initialize each LWLock, passing the new
       <literal>tranche_id</literal> as an argument:
@@ -3777,17 +3777,8 @@ void LWLockInitialize(LWLock *lock, int tranche_id)
      </para>
 
      <para>
-      Finally, each backend using the <literal>tranche_id</literal> should
-      associate it with a <literal>tranche_name</literal> by calling:
-<programlisting>
-void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
-</programlisting>
-     </para>
-
-     <para>
-      A complete usage example of <function>LWLockNewTrancheId</function>,
-      <function>LWLockInitialize</function>, and
-      <function>LWLockRegisterTranche</function> can be found in
+      A complete usage example of <function>LWLockNewTrancheId</function> and
+      <function>LWLockInitialize</function> can be found in
       <filename>contrib/pg_prewarm/autoprewarm.c</filename> in the
       <productname>PostgreSQL</productname> source tree.
      </para>

src/backend/postmaster/launch_backend.c

@@ -101,7 +101,7 @@ typedef struct
 	struct InjectionPointsCtl *ActiveInjectionPoints;
 #endif
 	int			NamedLWLockTrancheRequests;
-	NamedLWLockTranche *NamedLWLockTrancheArray;
+	char	  **NamedLWLockTrancheNames;
 	int		   *LWLockCounter;
 	LWLockPadded *MainLWLockArray;
 	slock_t    *ProcStructLock;
@@ -761,7 +761,7 @@ save_backend_variables(BackendParameters *param,
 #endif
 
 	param->NamedLWLockTrancheRequests = NamedLWLockTrancheRequests;
-	param->NamedLWLockTrancheArray = NamedLWLockTrancheArray;
+	param->NamedLWLockTrancheNames = NamedLWLockTrancheNames;
 	param->LWLockCounter = LWLockCounter;
 	param->MainLWLockArray = MainLWLockArray;
 	param->ProcStructLock = ProcStructLock;
@@ -1022,7 +1022,7 @@ restore_backend_variables(BackendParameters *param)
 #endif
 
 	NamedLWLockTrancheRequests = param->NamedLWLockTrancheRequests;
-	NamedLWLockTrancheArray = param->NamedLWLockTrancheArray;
+	NamedLWLockTrancheNames = param->NamedLWLockTrancheNames;
 	LWLockCounter = param->LWLockCounter;
 	MainLWLockArray = param->MainLWLockArray;
 	ProcStructLock = param->ProcStructLock;

src/backend/storage/ipc/dsm_registry.c

@@ -299,8 +299,7 @@ GetNamedDSA(const char *name, bool *found)
 		entry->type = DSMR_ENTRY_TYPE_DSA;
 
 		/* Initialize the LWLock tranche for the DSA. */
-		state->tranche = LWLockNewTrancheId();
-		LWLockRegisterTranche(state->tranche, name);
+		state->tranche = LWLockNewTrancheId(name);
 
 		/* Initialize the DSA. */
 		ret = dsa_create(state->tranche);
@@ -321,9 +320,6 @@ GetNamedDSA(const char *name, bool *found)
 			ereport(ERROR,
 					(errmsg("requested DSA already attached to current process")));
 
-		/* Initialize existing LWLock tranche for the DSA. */
-		LWLockRegisterTranche(state->tranche, name);
-
 		/* Attach to existing DSA. */
 		ret = dsa_attach(state->handle);
 		dsa_pin_mapping(ret);
@@ -378,8 +374,7 @@ GetNamedDSHash(const char *name, const dshash_parameters *params, bool *found)
 		entry->type = DSMR_ENTRY_TYPE_DSH;
 
 		/* Initialize the LWLock tranche for the hash table. */
-		dsh_state->tranche = LWLockNewTrancheId();
-		LWLockRegisterTranche(dsh_state->tranche, name);
+		dsh_state->tranche = LWLockNewTrancheId(name);
 
 		/* Initialize the DSA for the hash table. */
 		dsa = dsa_create(dsh_state->tranche);
@@ -409,9 +404,6 @@ GetNamedDSHash(const char *name, const dshash_parameters *params, bool *found)
 			ereport(ERROR,
 					(errmsg("requested DSHash already attached to current process")));
 
-		/* Initialize existing LWLock tranche for the hash table. */
-		LWLockRegisterTranche(dsh_state->tranche, name);
-
 		/* Attach to existing DSA for the hash table. */
 		dsa = dsa_attach(dsh_state->dsa_handle);
 		dsa_pin_mapping(dsa);