Re: Race between KeepFileRestoredFromArchive() and restartpoint

On Wed, Aug 03, 2022 at 11:24:17AM +0900, Kyotaro Horiguchi wrote:
> At Tue, 2 Aug 2022 16:03:42 -0500, Don Seiler <don@seiler.us> wrote in 
> > could not link file “pg_wal/xlogtemp.18799" to
> > > “pg_wal/000000010000D45300000010”: File exists

> Hmm.  It seems like a race condition betwen StartupXLOG() and
> RemoveXlogFIle(). We need wider extent of ContolFileLock. Concretely
> taking ControlFileLock before deciding the target xlog file name in
> RemoveXlogFile() seems to prevent this happening. (If this is correct
> this is a live issue on the master branch.)

RemoveXlogFile() calls InstallXLogFileSegment() with find_free=true.  The
intent of find_free=true is to make it okay to pass a target xlog file that
ceases to be a good target.  (InstallXLogFileSegment() searches for a good
target while holding ControlFileLock.)  Can you say more about how that proved
to be insufficient?