pgsql: Avoid possible deadlock while locking multiple heap pages. - Mailing list pgsql-committers

Avoid possible deadlock while locking multiple heap pages.

To avoid deadlock, backend acquires a lock on heap pages in block
number order.  In certain cases, lock on heap pages is dropped and
reacquired.  In this case, the locks are dropped for reading in
corresponding VM page/s. The issue is we re-acquire locks in bufferId
order whereas the intention was to acquire in blockid order.

This commit ensures that we will always acquire locks on heap pages in
blockid order.

Reported-by: Nishant Fnu
Author: Nishant Fnu
Reviewed-by: Amit Kapila and Robert Haas
Backpatch-through: 9.4
Discussion: https://postgr.es/m/5883C831-2ED1-47C8-BFAC-2D5BAE5A8CAE@amazon.com

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/073afae81989c0eec572c9f5850b9265c9e07933

Modified Files
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src/backend/access/heap/hio.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)