Improve some global variable declarations

We have in launch_backend.c:

    /*
     * The following need to be available to the save/restore_backend_variables
     * functions.  They are marked NON_EXEC_STATIC in their home modules.
     */
    extern slock_t *ShmemLock;
    extern slock_t *ProcStructLock;
    extern PGPROC *AuxiliaryProcs;
    extern PMSignalData *PMSignalState;
    extern pg_time_t first_syslogger_file_time;
    extern struct bkend *ShmemBackendArray;
    extern bool redirection_done;

That comment is not completely true: ShmemLock, ShmemBackendArray, and
redirection_done are not in fact NON_EXEC_STATIC.  ShmemLock once was,
but was then needed elsewhere.  ShmemBackendArray was static inside
postmaster.c before launch_backend.c was created.  redirection_done
was never static.

This patch moves the declaration of ShmemLock and redirection_done to
a header file.

ShmemBackendArray gets a NON_EXEC_STATIC.  This doesn't make a
difference, since it only exists if EXEC_BACKEND anyway, but it makes
it consistent.

After that, the comment is now correct.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/e0a62134-83da-4ba4-8cdb-ceb0111c95ce@eisentraut.org

src/backend/postmaster/launch_backend.c

@@ -672,13 +672,11 @@ SubPostmasterMain(int argc, char *argv[])
  * The following need to be available to the save/restore_backend_variables
  * functions.  They are marked NON_EXEC_STATIC in their home modules.
  */
-extern slock_t *ShmemLock;
 extern slock_t *ProcStructLock;
 extern PGPROC *AuxiliaryProcs;
 extern PMSignalData *PMSignalState;
 extern pg_time_t first_syslogger_file_time;
 extern struct bkend *ShmemBackendArray;
-extern bool redirection_done;
 
 #ifndef WIN32
 #define write_inheritable_socket(dest, src, childpid) ((*(dest) = (src)), true)

src/backend/postmaster/postmaster.c

@@ -179,7 +179,7 @@ typedef struct bkend
 static dlist_head BackendList = DLIST_STATIC_INIT(BackendList);
 
 #ifdef EXEC_BACKEND
-Backend    *ShmemBackendArray;
+NON_EXEC_STATIC Backend *ShmemBackendArray;
 #endif
 
 BackgroundWorker *MyBgworkerEntry = NULL;

src/backend/postmaster/syslogger.c

@@ -75,8 +75,6 @@ char	   *Log_filename = NULL;
 bool		Log_truncate_on_rotation = false;
 int			Log_file_mode = S_IRUSR | S_IWUSR;
 
-extern bool redirection_done;
-
 /*
  * Private state
  */

src/backend/storage/lmgr/lwlock.c

@@ -91,9 +91,6 @@
 #endif
 
 
-/* We use the ShmemLock spinlock to protect LWLockCounter */
-extern slock_t *ShmemLock;
-
 #define LW_FLAG_HAS_WAITERS			((uint32) 1 << 30)
 #define LW_FLAG_RELEASE_OK			((uint32) 1 << 29)
 #define LW_FLAG_LOCKED				((uint32) 1 << 28)
@@ -609,6 +606,7 @@ LWLockNewTrancheId(void)
 	int		   *LWLockCounter;
 
 	LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
+	/* We use the ShmemLock spinlock to protect LWLockCounter */
 	SpinLockAcquire(ShmemLock);
 	result = (*LWLockCounter)++;
 	SpinLockRelease(ShmemLock);

src/backend/utils/error/elog.c

@@ -95,8 +95,6 @@ ErrorContextCallback *error_context_stack = NULL;
 
 sigjmp_buf *PG_exception_stack = NULL;
 
-extern bool redirection_done;
-
 /*
  * Hook for intercepting messages before they are sent to the server log.
  * Note that the hook will not get called for messages that are suppressed

src/include/postmaster/postmaster.h

@@ -52,6 +52,7 @@ extern PGDLLIMPORT int postmaster_alive_fds[2];
 
 extern PGDLLIMPORT const char *progname;
 
+extern PGDLLIMPORT bool redirection_done;
 extern PGDLLIMPORT bool LoadedSSL;
 
 extern void PostmasterMain(int argc, char *argv[]) pg_attribute_noreturn();

src/include/storage/shmem.h

@@ -21,10 +21,12 @@
 #ifndef SHMEM_H
 #define SHMEM_H
 
+#include "storage/spin.h"
 #include "utils/hsearch.h"
 
 
 /* shmem.c */
+extern PGDLLIMPORT slock_t *ShmemLock;
 extern void InitShmemAccess(void *seghdr);
 extern void InitShmemAllocation(void);
 extern void *ShmemAlloc(Size size);