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3d474a0793
Fix some more violations of the "only straight-line code inside a spinlock" rule. These are hazardous not only because they risk holding the lock for an excessively long time, but because it's possible for palloc to throw elog(ERROR), leaving a stuck spinlock behind. copy_replication_slot() had two separate places that did pallocs while holding a spinlock. We can make the code simpler and safer by copying the whole ReplicationSlot struct into a local variable while holding the spinlock, and then referencing that copy. (While that's arguably more cycles than we really need to spend holding the lock, the struct isn't all that big, and this way seems far more maintainable than copying fields piecemeal. Anyway this is surely much cheaper than a palloc.) That bug goes back to v12. InvalidateObsoleteReplicationSlots() not only did a palloc while holding a spinlock, but for extra sloppiness then leaked the memory --- probably for the lifetime of the checkpointer process, though I didn't try to verify that. Fortunately that silliness is new in HEAD. pg_get_replication_slots() had a cosmetic violation of the rule, in that it only assumed it's safe to call namecpy() while holding a spinlock. Still, that's a hazard waiting to bite somebody, and there were some other cosmetic coding-rule violations in the same function, so clean it up. I back-patched this as far as v10; the code exists before that but it looks different, and this didn't seem important enough to adapt the patch further back. Discussion: https://postgr.es/m/20200602.161518.1399689010416646074.horikyota.ntt@gmail.com |
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PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.