Avoid SIGBUS on Linux when a DSM memory request overruns tmpfs. On Linux, shared memory segments created with shm_open() are backed by swap files created in tmpfs. If the swap file needs to be extended, but there's no tmpfs space left, you get a very unfriendly SIGBUS trap. To avoid this, force allocation of the full request size when we create the segment. This adds a few cycles, but none that we wouldn't expend later anyway, assuming the request isn't hugely bigger than the actual need.
Make this code #ifdef __linux__, because (a) there's not currently a reason to think the same problem exists on other platforms, and (b) applying posix_fallocate() to an FD created by shm_open() isn't very portable anyway. Back-patch to 9.4 where the DSM code came in. Thomas Munro, per a bug report from Amul Sul Discussion: https://postgr.es/m/1002664500.12301802.1471008223422.javamail.ya...@mail.yahoo.com Branch ------ REL9_5_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/05297416f362b50985b3cd3473778fbb0842295d Modified Files -------------- configure | 2 +- configure.in | 2 +- src/backend/storage/ipc/dsm_impl.c | 54 ++++++++++++++++++++++++++++++++++++-- src/include/pg_config.h.in | 3 +++ src/include/pg_config.h.win32 | 3 +++ 5 files changed, 60 insertions(+), 4 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers
