An InnoDB deadlock occurs when concurrent UPDATEs on a table with a composite (c,d) index generate conflicting GAP and Next‑Key locks during internal delete‑plus‑insert operations, and the simplest resolution is to drop column d from the index, leaving a single‑column index to prevent the lock clash.
This article examines a MySQL 5.6 InnoDB deadlock scenario caused by concurrent batch INSERTs, detailing the table schema, test cases, lock acquisition phases, log analysis, lock compatibility matrix, and discusses why typical SQL‑level fixes are limited, suggesting index redesign or data sharding as mitigation.
This article analyzes a MySQL deadlock scenario where concurrent inserts and unique‑key conflicts lead to circular lock waits, explains the underlying lock behavior, walks through the full deadlock log, and proposes using INSERT ON DUPLICATE KEY UPDATE to prevent the issue.
This article examines a real MySQL deadlock case caused by concurrent UPDATE‑then‑INSERT logic, explains the underlying InnoDB lock phases, analyzes the deadlock log step by step, and proposes a safer single‑statement solution using INSERT ON DUPLICATE KEY.
The article examines a MySQL 5.6 deadlock caused by concurrent sessions locking a row via a non‑unique index and the primary key in different orders, explains the circular wait illustrated in the log, and recommends updating rows using the primary key to enforce consistent lock ordering and prevent such deadlocks.
This article walks through a step‑by‑step InnoDB deadlock case where three sessions inserting rows with the same unique key cause a lock‑compatibility conflict, explains the INSERT lock phases, shows the actual deadlock log, and reveals why the deadlock occurs.
This article walks through MySQL InnoDB lock mechanisms, demonstrates how concurrent INSERTs on a unique key generate intention and gap locks, and uses detailed engine status logs to explain why those locks can cause deadlocks.
An in‑depth MySQL case study shows how concurrent gap‑locks under REPEATABLE READ can cause a deadlock when two transactions delete non‑existent rows and then attempt inserts, includes full DDL, log excerpts, step‑by‑step analysis, and practical mitigation strategies.
This article examines two MySQL deadlock scenarios under REPEATABLE READ isolation—one with a non‑unique index and another with a unique index—by presenting table definitions, test data, raw deadlock logs, and step‑by‑step analysis of lock acquisition and waiting, ultimately offering practical recommendations to avoid such deadlocks.
The guide explains MySQL/InnoDB deadlocks—how circular lock waits arise, the wait‑for‑graph detection that rolls back the transaction with fewer undo logs, the various lock modes and their behavior in UPDATE/INSERT/DELETE, and practical strategies such as proper indexing, consistent access order, and configuration tweaks to detect, handle, and prevent deadlocks.
This article explains MySQL shared (S) and exclusive (X) row‑level locks, demonstrates their behavior with two concurrent sessions, shows how lock ordering can cause deadlocks, and provides practical tips for using InnoDB locking correctly.
This article examines why concurrent upsert operations in a high‑throughput MySQL service can cause deadlocks due to GAP locks and phantom reads, explains the underlying InnoDB locking mechanisms, and offers practical solutions such as adjusting isolation levels or redesigning data sharding logic.
This article explains the concept of deadlocks, outlines the four necessary conditions, and provides a step‑by‑step guide using pstack and gdb on Linux to identify, analyze, and fix thread deadlocks, along with practical prevention techniques.
This article explains MySQL InnoDB locking mechanisms—including optimistic and pessimistic locks, shared and exclusive locks, row and table locks—and provides practical SQL examples and step‑by‑step guidance for detecting and resolving deadlocks in high‑concurrency environments.
This article introduces the four major categories of multithreaded bugs—data races, atomicity failures, ordering failures, and deadlocks—explains their causes with Java examples, and provides practical techniques such as using state machines, volatile variables, consistent lock ordering, and proper exception handling to prevent them.
This article provides a comprehensive overview of MySQL’s logical server architecture, lock types, transaction fundamentals, ACID properties, isolation levels, MVCC mechanisms, and deadlock handling, including practical SQL examples and strategies for ensuring data consistency and performance.
This article describes the background of Android thread freeze issues caused by deadlocks, presents a client‑server monitoring architecture that captures thread and lock information via system traces, details automated analysis methods for deadlock detection and non‑deadlock causes, and shares the observed performance improvements and future plans.
This article examines common MySQL concurrency problems—including table locks from MyISAM, metadata locks during online DDL, row‑level deadlocks, and lock‑wait timeouts—explains how to detect them with processlist and InnoDB status, and provides practical mitigation strategies.
This article examines typical MySQL concurrency problems—including table lock‑induced slow queries, metadata lock blocking during online schema changes, deadlock scenarios, and lock‑wait timeouts—provides step‑by‑step reproductions, analysis of lock behavior, and practical mitigation strategies such as using InnoDB, online DDL tools, and monitoring techniques.
The article analyzes a rare three‑thread deadlock caused by FLUSH TABLES WITH READ LOCK during parallel replication on MySQL 5.7, explains the MDL lock interactions, shows how to reproduce the issue, and provides practical kill‑thread and configuration solutions to avoid it.
This article analyzes a JVM deadlock issue encountered in a Tomcat-based application, detailing the problem's cause, analysis using jstack, and the solution involving ClassLoader isolation and ParallelCapable registration.
This article explains how to quickly locate and fix online MySQL problems such as partial update failures, InnoDB deadlocks, and lock‑wait timeouts by analyzing server logs, understanding InnoDB row‑lock behavior, optimizing indexes, adjusting transaction settings, and using a custom log‑collection script.
The article walks through a puzzling MySQL deadlock caused by two concurrent transactions on a table with a unique index, explains how to read the InnoDB status output, identifies the lock types and order, and shows a detailed step‑by‑step reconstruction of the deadlock scenario.
This article explains the concept of deadlocks, outlines the four necessary conditions, and demonstrates a step‑by‑step Linux workflow using pstack and gdb together with a sample pthread program to identify, analyze, and fix cross‑locking deadlock scenarios.
The article explains what deadlocks are, compares spinlocks and semaphores, describes typical deadlock scenarios in the Linux kernel, and details the built‑in detection mechanisms such as hung‑task (D‑state) and soft‑lockup (R‑state) along with the NMI watchdog for long interrupt disabling.
This article examines three real‑world MySQL deadlock incidents—unique‑key null insertion, concurrent duplicate‑key insertion, and a JDBC parameter bug—detailing their detection, analysis, and the concrete fixes applied to prevent recurrence.
A MySQL 5.5 server on CentOS 6.7 hung because two internal mutexes (LOCK_index and LOCK_thread_count) deadlocked during concurrent purge binlog and reset master commands, and the issue was resolved by upgrading to a version where the bug is fixed.
This article explains MySQL InnoDB's locking mechanisms—including MVCC snapshot vs. current reads, two‑phase locking, isolation levels, lock types, GAP locks, and deadlock scenarios—by analyzing simple and complex SQL examples and showing how different index and isolation configurations affect lock acquisition.
This article explains what a deadlock is, outlines its four necessary conditions, provides a sample pthread program that deadlocks, and shows step‑by‑step how to use pstack and gdb on Linux to identify the stuck threads and understand the root cause.
This article explains Oracle deadlock fundamentals, classifies row‑level and block‑level (ITL) deadlocks, shows how to read trace files in both single‑instance and RAC environments, and provides step‑by‑step simulations that reveal root causes and practical mitigation techniques.
This article explains how deadlocks arise in Linux kernels, compares spinlocks and semaphores, and details the kernel's built‑in D‑state, R‑state, and long‑interrupt‑disable detection mechanisms such as hung‑task, soft‑lockup, and NMI watchdog, including key code snippets.
A deep dive into a long‑standing PHP‑CGI deadlock that left deleted log files occupying disk space, explaining how signal‑unsafe functions caused the lock, how the issue was diagnosed with lsof, strace and gdb, and the practical steps to eliminate the deadlock.
This article explains the theory behind SQL Server's parallel execution, illustrates its performance gains with Amdahl's Law, lists operators that block parallelism, discusses configuration settings, warns of deadlocks and thread starvation, and presents practical MapReduce‑style optimizations for real‑world workloads.
This article analyzes a puzzling MySQL deadlock scenario where concurrent DELETE statements on a uniquely indexed row lead to a deadlock, explaining the lock modes, InnoDB's deadlock‑prevention strategy, and the conditions that make such deadlocks possible.
This article provides an in‑depth analysis of MySQL/InnoDB locking mechanisms, covering MVCC snapshot vs current reads, cluster indexes, two‑phase locking, isolation levels, lock behavior for simple and complex SQL statements, and practical deadlock diagnosis techniques.
The article explains how concurrent transactions can cause deadlocks when resources are locked, and introduces the Actor model—combining data, behavior, and message passing—to give data its own active logic, thereby naturally handling concurrency and avoiding such deadlocks.
A metaphorical story follows a newly created thread as it learns about extracting request parameters, performing login, handling CPU scheduling, using caches, encountering deadlocks, and ultimately witnessing a system reboot, illustrating core concepts of multithreading, concurrency control, and thread‑pool lifecycle.
This report details a series of MySQL InnoDB experiments that examine transaction locking, lock types, gap and next‑key locks, and deadlock behavior across various SQL operations, providing practical insights for optimizing concurrency and preventing deadlocks.
This article explains what a deadlock is, why it occurs, the four necessary conditions that enable it, and outlines common strategies—including ignoring, detection and recovery, avoidance, and prevention—to manage or eliminate deadlocks in operating systems.
