Pass MyPMChildSlot as an explicit argument to child process

All the other global variables passed from postmaster to child have
the same value in all the processes, while MyPMChildSlot is more like
a parameter to each child process.

Reviewed-by: Andres Freund <[email protected]>
Discussion: https://www.postgresql.org/message-id/a102f15f-eac4-4ff2-af02-f9ff209ec66f@iki.fi

diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 6ce75f6f77d50062a63b8b0bbfc5295312098ddc..1f2d829ec5a657f81cd95f0e5704d3e8dd7e471f 100644 (file)
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -88,7 +88,6 @@ typedef int InheritableSocket;
 typedef struct
 {
    char        DataDir[MAXPGPATH];
-   int         MyPMChildSlot;
 #ifndef WIN32
    unsigned long UsedShmemSegID;
 #else
@@ -130,6 +129,8 @@ typedef struct
    char        my_exec_path[MAXPGPATH];
    char        pkglib_path[MAXPGPATH];
 
+   int         MyPMChildSlot;
+
    /*
     * These are only used by backend processes, but are here because passing
     * a socket needs some special handling on Windows. 'client_sock' is an
@@ -151,13 +152,16 @@ typedef struct
 static void read_backend_variables(char *id, char **startup_data, size_t *startup_data_len);
 static void restore_backend_variables(BackendParameters *param);
 
-static bool save_backend_variables(BackendParameters *param, ClientSocket *client_sock,
+static bool save_backend_variables(BackendParameters *param, int child_slot,
+                                  ClientSocket *client_sock,
 #ifdef WIN32
                                   HANDLE childProcess, pid_t childPid,
 #endif
                                   char *startup_data, size_t startup_data_len);
 
-static pid_t internal_forkexec(const char *child_kind, char *startup_data, size_t startup_data_len, ClientSocket *client_sock);
+static pid_t internal_forkexec(const char *child_kind, int child_slot,
+                              char *startup_data, size_t startup_data_len,
+                              ClientSocket *client_sock);
 
 #endif                         /* EXEC_BACKEND */
 
@@ -215,11 +219,12 @@ PostmasterChildName(BackendType child_type)
  * appropriate, and fds and other resources that we've inherited from
  * postmaster that are not needed in a child process have been closed.
  *
- * 'startup_data' is an optional contiguous chunk of data that is passed to
- * the child process.
+ * 'child_slot' is the PMChildFlags array index reserved for the child
+ * process.  'startup_data' is an optional contiguous chunk of data that is
+ * passed to the child process.
  */
 pid_t
-postmaster_child_launch(BackendType child_type,
+postmaster_child_launch(BackendType child_type, int child_slot,
                        char *startup_data, size_t startup_data_len,
                        ClientSocket *client_sock)
 {
@@ -228,7 +233,7 @@ postmaster_child_launch(BackendType child_type,
    Assert(IsPostmasterEnvironment && !IsUnderPostmaster);
 
 #ifdef EXEC_BACKEND
-   pid = internal_forkexec(child_process_kinds[child_type].name,
+   pid = internal_forkexec(child_process_kinds[child_type].name, child_slot,
                            startup_data, startup_data_len, client_sock);
    /* the child process will arrive in SubPostmasterMain */
 #else                          /* !EXEC_BACKEND */
@@ -256,6 +261,7 @@ postmaster_child_launch(BackendType child_type,
         */
        MemoryContextSwitchTo(TopMemoryContext);
 
+       MyPMChildSlot = child_slot;
        if (client_sock)
        {
            MyClientSocket = palloc(sizeof(ClientSocket));
@@ -282,7 +288,8 @@ postmaster_child_launch(BackendType child_type,
  * - fork():s, and then exec():s the child process
  */
 static pid_t
-internal_forkexec(const char *child_kind, char *startup_data, size_t startup_data_len, ClientSocket *client_sock)
+internal_forkexec(const char *child_kind, int child_slot,
+                 char *startup_data, size_t startup_data_len, ClientSocket *client_sock)
 {
    static unsigned long tmpBackendFileNum = 0;
    pid_t       pid;
@@ -302,7 +309,7 @@ internal_forkexec(const char *child_kind, char *startup_data, size_t startup_dat
     */
    paramsz = SizeOfBackendParameters(startup_data_len);
    param = palloc0(paramsz);
-   if (!save_backend_variables(param, client_sock, startup_data, startup_data_len))
+   if (!save_backend_variables(param, child_slot, client_sock, startup_data, startup_data_len))
    {
        pfree(param);
        return -1;              /* log made by save_backend_variables */
@@ -391,7 +398,8 @@ internal_forkexec(const char *child_kind, char *startup_data, size_t startup_dat
  *  file is complete.
  */
 static pid_t
-internal_forkexec(const char *child_kind, char *startup_data, size_t startup_data_len, ClientSocket *client_sock)
+internal_forkexec(const char *child_kind, int child_slot,
+                 char *startup_data, size_t startup_data_len, ClientSocket *client_sock)
 {
    int         retry_count = 0;
    STARTUPINFO si;
@@ -472,7 +480,9 @@ retry:
        return -1;
    }
 
-   if (!save_backend_variables(param, client_sock, pi.hProcess, pi.dwProcessId, startup_data, startup_data_len))
+   if (!save_backend_variables(param, child_slot, client_sock,
+                               pi.hProcess, pi.dwProcessId,
+                               startup_data, startup_data_len))
    {
        /*
         * log made by save_backend_variables, but we have to clean up the
@@ -684,7 +694,8 @@ static void read_inheritable_socket(SOCKET *dest, InheritableSocket *src);
 
 /* Save critical backend variables into the BackendParameters struct */
 static bool
-save_backend_variables(BackendParameters *param, ClientSocket *client_sock,
+save_backend_variables(BackendParameters *param,
+                      int child_slot, ClientSocket *client_sock,
 #ifdef WIN32
                       HANDLE childProcess, pid_t childPid,
 #endif
@@ -701,7 +712,7 @@ save_backend_variables(BackendParameters *param, ClientSocket *client_sock,
 
    strlcpy(param->DataDir, DataDir, MAXPGPATH);
 
-   param->MyPMChildSlot = MyPMChildSlot;
+   param->MyPMChildSlot = child_slot;
 
 #ifdef WIN32
    param->ShmemProtectiveRegion = ShmemProtectiveRegion;

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 4129c71efad488a8a15b1af0e78b8160e394ec1b..78e66a06ac5874161202fdd14ed76b263ffe3c2e 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -3374,8 +3374,7 @@ BackendStartup(ClientSocket *client_sock)
    /* Hasn't asked to be notified about any bgworkers yet */
    bn->bgworker_notify = false;
 
-   MyPMChildSlot = bn->child_slot;
-   pid = postmaster_child_launch(bn->bkend_type,
+   pid = postmaster_child_launch(bn->bkend_type, bn->child_slot,
                                  (char *) &startup_data, sizeof(startup_data),
                                  client_sock);
    if (pid < 0)
@@ -3700,8 +3699,7 @@ StartChildProcess(BackendType type)
        return NULL;
    }
 
-   MyPMChildSlot = pmchild->child_slot;
-   pid = postmaster_child_launch(type, NULL, 0, NULL);
+   pid = postmaster_child_launch(type, pmchild->child_slot, NULL, 0, NULL);
    if (pid < 0)
    {
        /* in parent, fork failed */
@@ -3878,8 +3876,8 @@ StartBackgroundWorker(RegisteredBgWorker *rw)
            (errmsg_internal("starting background worker process \"%s\"",
                             rw->rw_worker.bgw_name)));
 
-   MyPMChildSlot = bn->child_slot;
-   worker_pid = postmaster_child_launch(B_BG_WORKER, (char *) &rw->rw_worker, sizeof(BackgroundWorker), NULL);
+   worker_pid = postmaster_child_launch(B_BG_WORKER, bn->child_slot,
+                                        (char *) &rw->rw_worker, sizeof(BackgroundWorker), NULL);
    if (worker_pid == -1)
    {
        /* in postmaster, fork failed ... */

diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 7ca24c66634695d59aa4880b576ad31ffcf6177a..f12639056f2bfc7d462f08ee738ff7a163794c38 100644 (file)
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -694,14 +694,15 @@ SysLogger_Start(int child_slot)
        pfree(filename);
    }
 
-   MyPMChildSlot = child_slot;
 #ifdef EXEC_BACKEND
    startup_data.syslogFile = syslogger_fdget(syslogFile);
    startup_data.csvlogFile = syslogger_fdget(csvlogFile);
    startup_data.jsonlogFile = syslogger_fdget(jsonlogFile);
-   sysloggerPid = postmaster_child_launch(B_LOGGER, (char *) &startup_data, sizeof(startup_data), NULL);
+   sysloggerPid = postmaster_child_launch(B_LOGGER, child_slot,
+                                          (char *) &startup_data, sizeof(startup_data), NULL);
 #else
-   sysloggerPid = postmaster_child_launch(B_LOGGER, NULL, 0, NULL);
+   sysloggerPid = postmaster_child_launch(B_LOGGER, child_slot,
+                                          NULL, 0, NULL);
 #endif                         /* EXEC_BACKEND */
 
    if (sysloggerPid == -1)

diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index a55e7a79fa4ab822c64a1c7fecab3d70916b97a3..f05eb1c470b51757ca717adc83a7cf7bf9a08689 100644 (file)
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -108,6 +108,7 @@ extern PGDLLIMPORT struct ClientSocket *MyClientSocket;
 
 /* prototypes for functions in launch_backend.c */
 extern pid_t postmaster_child_launch(BackendType child_type,
+                                    int child_slot,
                                     char *startup_data,
                                     size_t startup_data_len,
                                     struct ClientSocket *client_sock);