pg_signal_backend_asymmetry.v2.diff

diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
new file mode 100644
index f3c7860..c491783
*** a/src/backend/utils/adt/misc.c
--- b/src/backend/utils/adt/misc.c
*************** current_query(PG_FUNCTION_ARGS)
*** 88,125 ****
  static int
  pg_signal_backend(int pid, int sig)
  {
! 	PGPROC	   *proc;
  
! 	if (!superuser())
  	{
  		/*
! 		 * Since the user is not superuser, check for matching roles. Trust
! 		 * that BackendPidGetProc will return NULL if the pid isn't valid,
! 		 * even though the check for whether it's a backend process is below.
! 		 * The IsBackendPid check can't be relied on as definitive even if it
! 		 * was first. The process might end between successive checks
! 		 * regardless of their order. There's no way to acquire a lock on an
! 		 * arbitrary process to prevent that. But since so far all the callers
! 		 * of this mechanism involve some request for ending the process
! 		 * anyway, that it might end on its own first is not a problem.
  		 */
! 		proc = BackendPidGetProc(pid);
! 
! 		if (proc == NULL || proc->roleId != GetUserId())
! 			return SIGNAL_BACKEND_NOPERMISSION;
  	}
  
! 	if (!IsBackendPid(pid))
  	{
  		/*
! 		 * This is just a warning so a loop-through-resultset will not abort
! 		 * if one backend terminated on it's own during the run
  		 */
! 		ereport(WARNING,
! 				(errmsg("PID %d is not a PostgreSQL server process", pid)));
! 		return SIGNAL_BACKEND_ERROR;
  	}
  
  	/*
  	 * Can the process we just validated above end, followed by the pid being
  	 * recycled for a new process, before reaching here?  Then we'd be trying
--- 88,124 ----
  static int
  pg_signal_backend(int pid, int sig)
  {
! 	PGPROC	   *proc = BackendPidGetProc(pid);
  
! 	/* Trust that BackendPidGetProc will return NULL if the pid isn't valid.
! 	 * Note, this check can't be relied on as definitive even if it
! 	 * was first. The process might end between successive checks
! 	 * regardless of their order. There's no way to acquire a lock on an
! 	 * arbitrary process to prevent that. But since so far all the callers
! 	 * of this mechanism involve some request for ending the process
! 	 * anyway, that it might end on its own first is not a problem.
! 	 */
! 	if (proc == NULL)
  	{
  		/*
! 		 * This is just a warning so a loop-through-resultset will not abort
! 		 * if one backend terminated on its own during the run.
  		 */
! 		ereport(WARNING,
! 				(errmsg("PID %d is not a PostgreSQL server process", pid)));
! 		return SIGNAL_BACKEND_ERROR;
  	}
  
! 	if (!superuser())
  	{
  		/*
! 		 * Since the user is not superuser, check for matching roles.
  		 */
! 		if (proc->roleId != GetUserId())
! 			return SIGNAL_BACKEND_NOPERMISSION;
  	}
  
+ 
  	/*
  	 * Can the process we just validated above end, followed by the pid being
  	 * recycled for a new process, before reaching here?  Then we'd be trying