Re: Cleanup: PGProc->links doesn't need to be the first field anymore

Hi,

On 2024-07-04 01:54:18 +0300, Heikki Linnakangas wrote:
> pgproc.h has this:
> 
> > struct PGPROC
> > {
> > 	/* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */
> > 	dlist_node	links;			/* list link if process is in a list */
> > 	dlist_head *procgloballist; /* procglobal list that owns this PGPROC */
> > ...
> 
> I don't see any particular reason for 'links' to be the first field. We used
> to do things like "proc = (PGPROC *) waitQueue->links.next", but since
> commit 5764f611e1, this has been a "dlist", and dlist_container() can handle
> the list link being anywhere in the struct.

Indeed.


> I tried moving it and ran the regression tests. That revealed one place
> where we still don't use dlist_container:
> 
> > 	if (!dlist_is_empty(procgloballist))
> > 	{
> > 		MyProc = (PGPROC *) dlist_pop_head_node(procgloballist);
> > ...
> 
> I believe that was just an oversight. Trivial patch attached.

Oops. Yes, I clearly should have used dlist_container() here.


+1

Greetings,

Andres Freund