Commit 86db52a506 changed the locking of injection points to use only
atomic ops and spinlocks, to make it possible to define injection
points in processes that don't have a PGPROC entry (yet). However, it
didn't work in EXEC_BACKEND mode, because the pointer to shared memory
area was not initialized until the process "attaches" to all the
shared memory structs. To fix, pass the pointer to the child process
along with other global variables that need to be set up early.
Backpatch-through: 17
To avoid the compiler warnings:
launch_backend.c:211:39: warning: comparison of constant 16 with expression of type 'BackendType' (aka 'enum BackendType') is always true [-Wtautological-constant-out-of-range-compare]
launch_backend.c:233:39: warning: comparison of constant 16 with expression of type 'BackendType' (aka 'enum BackendType') is always true [-Wtautological-constant-out-of-range-compare]
The point of the assertions was to fail more explicitly if someone
adds a new BackendType to the end of the enum, but forgets to add it
to the child_process_kinds array. It was a pretty weak assertion to
begin with, because it wouldn't catch if you added a new BackendType
in the middle of the enum. So let's just remove it.
Per buildfarm member ayu and a few others, spotted by Tom Lane.
Discussion: https://www.postgresql.org/message-id/4119680.1710913067@sss.pgh.pa.us
Introduce new postmaster_child_launch() function that deals with the
differences in EXEC_BACKEND mode.
Refactor the mechanism of passing information from the parent to child
process. Instead of using different command-line arguments when
launching the child process in EXEC_BACKEND mode, pass a
variable-length blob of startup data along with all the global
variables. The contents of that blob depend on the kind of child
process being launched. In !EXEC_BACKEND mode, we use the same blob,
but it's simply inherited from the parent to child process.
Reviewed-by: Tristan Partin, Andres Freund
Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
This just moves the functions, with no other changes, to make the next
commits smaller and easier to review. The moved functions are related
to launching postmaster child processes in EXEC_BACKEND mode.
Reviewed-by: Tristan Partin, Andres Freund
Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
