bufmgr: Fix ordering of checks in PinBuffer()
The check for skip_if_not_valid added in 819dc118c0f6 was put at the start of
the loop. A CAS loop in theory does allow to make that check in a race free
manner. However, just after the check, there's a
old_buf_state = WaitBufHdrUnlocked(buf);
which introduces a race, because it would allow BM_VALID to be cleared, after
the skip_if_not_valid check.
Fix by restarting the loop after WaitBufHdrUnlocked().
Reported-by: Yura Sokolov <[email protected]>
Discussion:
https://postgr.es/m/[email protected]
Branch
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master
Details
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https://git.postgresql.org/pg/commitdiff/c0af4eb4e71ecd4826ae6c9985f1d10ace5e1be6
Modified Files
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src/backend/storage/buffer/bufmgr.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
