pgsql: Fix bogus coding in WaitForBackgroundWorkerShutdown().

Fix bogus coding in WaitForBackgroundWorkerShutdown().

Some conditions resulted in "return" directly out of a PG_TRY block,
which left the exception stack dangling, and to add insult to injury
failed to restore the state of set_latch_on_sigusr1.

This is a bug only in 9.5; in HEAD it was accidentally fixed by commit
db0f6cad4, which removed the surrounding PG_TRY block. However, I (tgl)
chose to apply the patch to HEAD as well, because the old coding was
gratuitously different from WaitForBackgroundWorkerStartup(), and there
would indeed have been no bug if it were done like that to start with.

Dmitry Ivanov

Discussion: <1637882(dot)WfYN5gPf1A(at)abook>

Branch
------
REL9_5_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/c1d6ee879285969a93f244e08a3ff2344d2cd7ff

Modified Files
--------------
src/backend/postmaster/bgworker.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)