http://doxygen.postgresql.org/xlog_8c_source.html#l08197
On line 8197 of xlog.c:
08194 /* Get a local copy of the last safe checkpoint record. */
08195 SpinLockAcquire(&xlogctl->info_lck);
08196 lastCheckPointRecPtr = xlogctl->lastCheckPointRecPtr;
08197 memcpy(&lastCheckPoint, &XLogCtl->lastCheckPoint, sizeof(CheckPoint));
08198 SpinLockRelease(&xlogctl->info_lck);
Note the use of capital XLogCtl->lastCheckPoint, which is not the
volatile pointer.
I found this while scouring the code trying to figure out Bug #6291,
which is the (to my latest knowledge) is when the epoch is not
incremented (sometimes) when passing wraparound.
--
fdr
