Re: Lock release leak in pool_search_relcache

> While looking into src/utils/pool_relcache.c for other reasons, I
> noticed pool_search_relcache does not release lock in a certain code
> path. When the local relation cache does not hit, it searches the
> shared relation cache if enable_shared_relcache is on. If the lock for
> query cache has been already held (thus the variable "locked" is set
> to true), it acquires a shared lock, then releases it and acquires an
> exclusive lock to call pool_catalog_commit_cache. Since in this code
> path variable "locked" is set to true, subsequent code:
>
> if (pool_config->enable_shared_relcache && !locked)
> {
> pool_shmem_unlock();
> POOL_SETMASK(&oldmask);
> }
>
> does not reach inside the if statement -- lock is not released. I
> think to fix this, the following code requires "locked = false;"
>
> pool_shmem_unlock();
> pool_shmem_lock(POOL_MEMQ_EXCLUSIVE_LOCK);
> pool_catalog_commit_cache(backend, query, query_cache_data, query_cache_len);
>
> Attached patch does this. Plus following changes are made in the patch:
>
> - the variable name "locked" is confusing. To clarify the role of the
> variable, its name is changed to "locked_by_others".
>
> - Fix per_node_statement_log is called even though actual query is
> not sent to backend.

Pushed down to v4.4 stable.

Best regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
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