Recompute stack base in forked postmaster children.

This is for the benefit of running postgres under the rr
debugger. When using rr signal handlers running while a syscall is
active use an alternative stack. As e.g. bgworkers are started from
within signal handlers, the forked backend then has a different stack
base than postmaster. Previously that subsequently lead to those
processes triggering spurious "stack depth limit exceeded" errors.

Discussion: https://postgr.es/m/20200327182217.ubrrl32lyfhxfwk5@alap3.anarazel.de

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 73d278f3b2ccecb4c826eb049b1583cbaa9cc6fd..0578e92ba9c416d74693753e6083886db3227566 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -4900,11 +4900,6 @@ SubPostmasterMain(int argc, char *argv[])
        /* Close the postmaster's sockets (as soon as we know them) */
        ClosePostmasterPorts(strcmp(argv[1], "--forklog") == 0);
 
-       /*
-        * Set reference point for stack-depth checking
-        */
-       set_stack_base();
-
        /*
         * Set up memory area for GSS information. Mirrors the code in ConnCreate
         * for the non-exec case.

diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index a7b7b12249d7551b42e5b233068403044c27bec9..6fe25c023a4e2da852cac6d4e81d85148e8f0dac 100644 (file)
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -92,6 +92,15 @@ InitPostmasterChild(void)
 {
        IsUnderPostmaster = true;       /* we are a postmaster subprocess now */
 
+       /*
+        * Set reference point for stack-depth checking. We re-do that even in the
+        * !EXEC_BACKEND case, because there are some edge cases where processes
+        * are started with an alternative stack (e.g. starting bgworkers when
+        * running postgres using the rr debugger, as bgworkers are launched from
+        * signal handlers).
+        */
+       set_stack_base();
+
        InitProcessGlobals();
 
        /*