On Fri, Jan 6, 2012 at 6:13 AM, Magnus Hagander <magnus@hagander.net> wrote:
On Thu, Jan 5, 2012 at 23:19, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Magnus Hagander <magnus@hagander.net> writes: >> On Thu, Jan 5, 2012 at 17:13, Tom Lane <tgl@sss.pgh.pa.us> wrote: >>> I think link(2) would create race conditions of its own. I'd be >>> inclined to suggest that maybe we should just special-case a zero length >>> postmaster.pid file as meaning "okay to proceed". In general, garbage > >> That's pretty much what I meant - but with a warning message. > > Actually ... wait a minute. If we allow that, don't we create a race > condition between two postmasters starting at almost the same instant? > The second one could see the lock file when the first has created but > not yet filled it.
Good point, yeah, it should do that. But I still think it's rare enough that just special-casing the error message should be enough...
so just something that does like
stat(filename, &st);
size = st.st_size;
if (size == 0)
elog(ERROR, "lock file \"%s\" has 0 length.", filename);
