## +21 ## Hazard Pointer Synchronous Reclamation Beyond Concurrency TS2 ## MAGED MICHAEL ## Basic Hazard Pointer Algorithm Hazard pointers protect access to objects that may be removed concurrently concurrently. A hazard pointer is a single-writer multi-reader pointer. If a hazard pointer points to an object before its removal, then the object will not be reclaimed as long as the hazard pointer remains unchanged _3.jpg)  read pointer A from SRC SRC $$ ^{*}A $$ ![Image](/uploads/documents/1/7/5/a/175a94ae744d634a4a2d21a0d05b187f/p2_5

Restore, Then More! ## EDUARDO MADRID ## 2024 September 15 - 20 ## Let's do the opposite of pointer chasing Alternative title ## What's what we mean to improve? • Our systems need objects to arrays • ...word salad? ## Row-wise representation Heterogeneous (different) data types int id; Pointer. Can it be null? Optional? double price; Specials *specials; Category *category; bool is_homemade;

we already have a Concurrency TS? • Why do we need a new one? • implementation status 2.TS2 Hazard Pointer • how I learn to love C++ tricks ### 3. TS2 RCU • From C to C++ in 2500 days ![Image](/u Procrastinate away! Use Structured Deferral 4. Shared ptr vs atomic shared ptr vs hazard pointers vs Read 5.Hazard Pointers 6. Read Copy Update 7.A Concurrency Toolkit for C++ ![Image](/uploads/d synchronization primitives for locked-free programming on concurrent data structures. These are cell, hazard ptr and RCU. These extend the existing shared_ptr and the proposed atomic_shared_ptr which all have

September 15 - 20 ## Agenda 1. Improving C++20 Atomic Min/Max(P0493; Michael) 2. Hazard pointer extensions (P3135; Maged) 3. Pointer tagging (P3125; Maged) 4. Parallel Range algorithms (P3179; Michael), may benefits Additional functions for more specific needs ## Hazard Pointer Extensions beyond C++26 ## Hazard Pointers in C++26 -- Background Hazard pointers protect dynamic objects from being reclaimed, allowing jpg) ## Hazard Pointers C++26 template > class hazard_pointer_obj_base { void retire(D d = D()) noexcept; }; class hazard_pointer { hazard_pointer()

pg_lsn Type The pg_lsn data type can be used to store LSN (Log Sequence Number) data which is a pointer to a location in the WAL. This type is a representation of XLogRecPtr and an internal system type exact match in the set of operators considered), use it. Lack of an exact match creates a security hazard when calling, via qualified name 1 (not typical), any operator found in a schema that permits untrusted If exactly one candidate passes this test, use it. Otherwise, fail. Some examples follow. 1 The hazard does not arise with a non-schema-qualified name, because a search path containing schemas that permit

pg_Isn Type The pg_lsn data type can be used to store LSN (Log Sequence Number) data which is a pointer to a location in the WAL. This type is a representation of XLogRecPtr and an internal system type exact match in the set of operators considered), use it. Lack of an exact match creates a security hazard when calling, via qualified name $ {}^{1} $ (not typical), any operator found in a schema that two functions are in the same schema, the non-variadic one is preferred. This creates a security hazard when calling, via qualified name $ {}^{2} $ , a variadic function found in a schema that permits

pg\_Isn Type The pg_lsn data type can be used to store LSN (Log Sequence Number) data which is a pointer to a location in the WAL. This type is a representation of XLogRecPtr and an internal system type exact match in the set of operators considered), use it. Lack of an exact match creates a security hazard when calling, via qualified name $ {}^{1} $ (not typical), any operator found in a schema. that two functions are in the same schema, the non-variadic one is preferred. This creates a security hazard when calling, via qualified name $ {}^{2} $ , a variadic function found in a schema that permits

pg\_Isn Type The pg_lsn data type can be used to store LSN (Log Sequence Number) data which is a pointer to a location in the WAL. This type is a representation of XLogRecPtr and an internal system type exact match in the set of operators considered), use it. Lack of an exact match creates a security hazard when calling, via qualified name $ {}^{1} $ (not typical), any operator found in a schema that two functions are in the same schema, the non-variadic one is preferred. This creates a security hazard when calling, via qualified name $ {}^{2} $ , a variadic function found in a schema that permits

(thankfully) not used by either implementation • Both use the lowest-order bits on the control_block pointer as a lock shared_ptr load() { void store(shared_ptr desired) { with lock project on GitHub by Vladislav Tyulbashev Key idea: If we could atomically load the control_block pointer and increment the reference count at the same time, we would avoid the race to zero Carnegie Mellon Big idea: local_ref_count counts the number of in-flight atomic loads on the currently stored pointer ## Solution #2: The split reference count counted_cb increment_local_ref_count()

1. Arrays .....833 33.4.4.3.2. Structures .....834 33.4.4.3.3. Type也曾 .....835 33.4.4.3.4. Pointer .....836 33.4.5. Handling Nonprimitive SQL Data Types .....836 33.4.5.1. Arrays .....836 33.4 pg\_Isn Type The pg_lsn data type can be used to store LSN (Log Sequence Number) data which is a pointer to a location in the XLOG. This type is a representation of XLogRecPtr and an internal system type exact match in the set of operators considered), use it. Lack of an exact match creates a security hazard when calling, via qualified name $ {}^{1} $ (not typical), any operator found in a schema that