This article examines a MySQL deadlock case involving DELETE and UPDATE statements, explains why the primary key index is locked despite non‑key predicates, analyzes execution plans and optimizer trace, and proposes index restructuring and query hints to resolve the issue.
This article explains why MySQL needs locking, details every InnoDB lock type—including shared, exclusive, intention, record, gap, next‑key, insert‑intention and auto‑increment locks—covers lock compatibility, deadlock causes and prevention, compares optimistic and pessimistic locking, and shows how SELECT FOR UPDATE behaves under different isolation levels.
During a computer freeze, the CPU isn’t simply idle; it may be trapped in a high‑priority interrupt handler or deadlocked kernel code, and the operating system’s scheduling and interrupt priorities determine whether the processor can be reclaimed, explaining why a simple infinite loop rarely causes a crash.
This article explains why computers freeze, describing how the CPU can become stuck in software loops, the crucial role of interrupts and their priorities, and how kernel‑level deadlocks can render a system unresponsive despite the CPU still running.
This article analyzes a production deadlock caused by MyBatis‑Plus’s saveOrUpdate method, explains how MySQL gap locks lead to the issue, demonstrates reproducible tests, and offers practical solutions such as disabling gap locks or customizing the saveOrUpdate implementation.
During a massive 618 promotion, the system’s BulkProcessor for Elasticsearch suffered deadlocks caused by competing lock acquisition between MQ consumer threads and internal scheduler threads, leading to paused message consumption; the article details the root cause, thread analysis, and two practical solutions.
The article investigates a deadlock caused by Elasticsearch BulkProcessor during massive MQ message processing, explains how thread‑pool contention and retry logic lead to lock starvation, and proposes version upgrades or disabling retries to restore stable consumption.
This article explains how to locate Java deadlocks by using command‑line tools such as jps and jstack, the ThreadMXBean API’s findDeadlockedThreads method, and online utilities like FastThread and JStack Review, while also offering guidance on preventing and fixing deadlocks in production.
This article investigates how the MyBatis‑Plus saveOrUpdate method can trigger gap‑lock deadlocks in MySQL, explains the underlying concepts of deadlocks and gap locks, reproduces the issue with concrete SQL scripts, and proposes both risky and recommended mitigation strategies.
This article examines a MySQL deadlock caused by concurrent INSERT operations on a unique index, detailing the detection, reproduction, root cause analysis using InnoDB status, performance_schema data, and provides scripts and recommendations to trace and resolve such deadlocks.
This article examines how common business operations using SELECT ... FOR UPDATE and INSERT can cause MySQL Next‑Key lock deadlocks, explains the underlying gap‑lock and row‑lock mechanisms, demonstrates practical experiments, and proposes strategies such as postponing locks or using primary‑key updates to avoid such deadlocks.
This article examines how common business operations using SELECT ... FOR UPDATE and INSERT can cause Next‑Key lock deadlocks in MySQL under repeatable‑read isolation, demonstrates the locking behavior with practical SQL examples, and proposes strategies such as post‑locking and primary‑key updates to prevent such deadlocks.
This article explains what a deadlock is, demonstrates a simple Java deadlock example with code, outlines the four necessary conditions, and introduces four practical tools—jstack, jconsole, jvisualvm, and jmc—for diagnosing and resolving deadlocks in Java applications.
This article explains why MySQL needs locking, details every InnoDB lock type—including shared, exclusive, intention, record, gap, next‑key, insert‑intention and auto‑increment locks—shows how they interact, and provides practical guidance for avoiding deadlocks and safely updating rows.
This article explains the fundamentals of Java threading, covering process vs thread differences, context switching, daemon and user threads, thread states, synchronization mechanisms, interruption handling, and deadlock detection with concrete code examples and visual illustrations.
The article details a step‑by‑step investigation of an intermittent deadlock occurring during session creation in a video‑conference system, explains how InnoDB lock types caused the conflict between DELETE and INSERT statements on the session and session_endpoint tables, reproduces the issue, debugs MySQL source code, and presents a simple code‑order fix to eliminate the deadlock.
A detailed investigation of intermittent MySQL InnoDB deadlocks occurring during video‑conference session creation, covering log extraction, lock analysis, source‑code debugging, reproducible test cases, and a simple code change that eliminates the deadlock while explaining the underlying locking mechanisms.
This guide explains how to detect MySQL deadlock exceptions, retrieve and interpret InnoDB deadlock logs and binlog files, and use the information to pinpoint conflicting SQL statements and fix the underlying lock issues in live systems.
This article explains practical JVM tuning scenarios—including how to identify and resolve excessive CPU consumption, thread deadlocks, and memory leaks—by using Linux tools such as top, jstack, jps, jstat, and jmap, and by analyzing heap dumps with Eclipse MAT.
The article explains how converting a serial RPC call layer to an asynchronous parallel model can cause thread pool exhaustion and hunger lock when tasks depend on each other, demonstrates the issue with Java code, and provides practical strategies such as using separate pools or CompletableFuture to avoid the problem.
This article explains Java multithreading safety issues, demonstrates synchronized methods, blocks, static methods, mutex locks, deadlock scenarios, and the differences between wait() and sleep() with clear code examples and analysis of their effects on thread execution.
When a computer freezes, it isn’t simply “stuck”; the CPU may be trapped in a loop, waiting on an interrupt, or blocked by a high‑priority kernel lock, and understanding interrupts, priority levels, and kernel deadlocks reveals why a dead loop alone rarely crashes the system.
The article explains that computer freezes are usually caused by software-level issues where the CPU gets trapped due to interrupt handling or kernel deadlocks, rather than hardware failure, and shows why a simple infinite loop cannot crash a modern operating system.
The article explains why computers appear to freeze by describing how the CPU, pre‑emptive multitasking, interrupt handling, and kernel‑level deadlocks interact, showing that simple infinite loops rarely cause a crash while kernel bugs can make the system unresponsive.
This article walks through a real MySQL deadlock scenario, explaining the four necessary deadlock conditions, illustrating how Next‑Key locks on non‑unique indexes cause gap locks, and presenting step‑by‑step analysis, experimental verification, and practical recommendations to avoid such deadlocks in production systems.
An in‑depth analysis of a deadlock caused by Go’s sync.RWMutex in a microservice, comparing its non‑reentrant read‑write lock behavior with Java’s ReentrantReadWriteLock, illustrating the root cause, code examples, and design rationale behind Go’s lock implementation.
This article investigates why S‑type GAP locks appear in deadlocks under the READ COMMITTED isolation level in MySQL InnoDB, detailing the transaction workflow, lock acquisition during INSERT operations, lock inheritance after rollbacks, and reproducing the deadlock scenario with code examples and diagrams.
This comprehensive guide explains operating system fundamentals, covering concurrency, process and thread management, scheduling algorithms, memory management techniques, device handling, deadlock detection, and classic synchronization problems with clear examples and code snippets.
This article details the technical challenges DingTalk faced when integrating Flutter across macOS and Windows desktops, covering memory leaks, shutdown deadlocks, OpenGL crashes, rendering glitches, plugin registration wild‑pointer crashes, and white‑screen issues, and explains the root causes and concrete solutions applied to each problem.
This article explains the root causes of thread‑safety problems in Java producer‑consumer scenarios, demonstrates how race conditions and deadlocks arise, and provides step‑by‑step solutions using synchronized blocks, wait/notify, notifyAll, and explicit Lock with Condition objects.
This article provides a comprehensive overview of operating system fundamentals, covering concepts such as concurrency, shared resources, virtual memory, process and thread management, synchronization mechanisms, classic synchronization problems, memory paging and replacement algorithms, device management, disk scheduling, and deadlock detection and prevention.
This article walks through implementing a global HashMap in Rust with lazy_static and RwLock, demonstrates common deadlock pitfalls when mixing read and write guards, and provides revised code that separates lifetimes to safely retrieve and remove entries without hanging.
The article explains MySQL InnoDB lock scopes and modes—including record, gap, next‑key and insert‑intention locks—illustrates a deadlock caused by concurrent inserts on a distributed lock table, and recommends limiting concurrency, sharding by business key, and splitting lock operations into smaller sub‑transactions to avoid such deadlocks.
This article explains the differences between processes and threads, outlines process states, describes inter‑process communication methods, details memory allocation strategies and page‑replacement algorithms, covers file allocation techniques, disk I/O scheduling, and outlines deadlock conditions and prevention methods.
This article walks through reproducing a MySQL deadlock in a test environment, explains how to read InnoDB status logs to pinpoint the conflicting locks, and offers practical tips to prevent deadlocks in production systems.
Learn practical JVM tuning techniques by identifying high CPU usage, diagnosing deadlocks, and uncovering memory leaks using tools such as top, jstack, jps, jstat, and jmap, with step‑by‑step commands and code examples to help you optimize Java application performance.
This article analyzes a production MySQL deadlock caused by two identical UPDATE statements that trigger an index‑merge optimization, explains the lock interactions between the idx_status and PRIMARY indexes, and provides code‑level and MySQL‑level solutions to prevent such deadlocks.
The article explains how MySQL 8.0 improves deadlock logging by showing lock information for the holding transaction, discusses potential misunderstandings, and provides a step‑by‑step reproduction of a deadlock case with SQL statements and detailed lock analysis.
This article explains why Python's subprocess.Popen can deadlock when the child process writes more data than the system pipe buffer (typically 4 MiB), and demonstrates practical solutions such as avoiding PIPE, using communicate(), and streaming output with StringIO to prevent the blockage.
This article explains MySQL InnoDB lock types, analyzes common deadlock scenarios with detailed SQL examples, describes the underlying locking mechanisms such as next‑key and gap locks, and provides practical prevention and resolution techniques for developers working with transactional databases.
This article explains the four necessary conditions that cause deadlocks, outlines four major strategies to prevent or resolve them, and provides a step‑by‑step MySQL example with code snippets and diagrams illustrating how deadlocks occur and can be avoided.
This article explains Java deadlocks with synchronized and Lock examples, outlines the four necessary conditions, introduces detection tools such as jstack, jconsole, jvisualvm and jmc, and presents practical solutions including sequential locking and polling lock techniques with optimizations to avoid loops and starvation.
This article investigates a deadlock between the Main Thread and the JavaScriptCore Heap Collector Thread on iOS 13, explains the underlying mutex and RunLoop interactions, reproduces the issue with CFTimer‑based timers, and proposes an AutoReleasePool‑wrapped solution along with best‑practice recommendations for JavaScriptCore usage.
This article examines MySQL’s locking mechanisms—including shared and exclusive row locks, gap and next‑key locks, table‑level and metadata locks—detailing how different SQL statements and index types affect lock acquisition, illustrating lock behavior with examples, and offering practical strategies to avoid deadlocks.
An in‑depth analysis reveals how a Main Thread and JavaScriptCore Heap Collector Thread can deadlock on iOS 13 due to RunLoop lock contention triggered by timer callbacks and AutoReleasePool memory reclamation, and provides a practical solution using scoped AutoReleasePool blocks to prevent the issue.
This article explains MySQL deadlocks, describes InnoDB lock types, shows how to read deadlock logs, analyzes classic concurrency cases, and offers practical tips to design indexes and write SQL that minimize lock conflicts and avoid deadlocks.
The article investigates a MySQL 8.0.18 replication deadlock caused by numerous set global read_only commands, explains the lock‑waiting chain involving global read and commit locks, reproduces two deadlock scenarios, and proposes practical solutions such as killing offending sessions or disabling slave_preserve_commit_order.
This article explains the root causes of MySQL deadlocks in InnoDB, walks through transaction and lock fundamentals, analyzes real‑world log cases, and presents practical solutions such as adjusting isolation levels, using SELECT FOR UPDATE, adding unique indexes, or checking existence before deletion to eliminate deadlocks.
This article explains why MySQL deadlocks occur in a test module, details table and row lock mechanisms, reproduces the deadlock scenario with two sessions, analyzes lock logs, and provides a solution by adding a composite index to prevent the conflict.
This article examines a real‑world MySQL deadlock caused by the Index Merge optimizer, explains InnoDB's lock‑on‑index mechanism, walks through the deadlock logs, and presents four practical solutions including force‑index hints, disabling Index Merge, creating a composite index, and a two‑step update approach.
This article explains MySQL's lock granularity (table, row, page), the different lock modes such as next‑key, gap and record locks, illustrates common deadlock scenarios with detailed SQL examples, and discusses InnoDB's deadlock prevention strategies and best‑practice solutions.
This article explains MySQL's table, row, and page lock levels, describes next‑key, gap, and record locks, illustrates common deadlock scenarios with detailed SQL examples, and outlines InnoDB's lock acquisition and deadlock‑prevention strategies to help developers avoid concurrency issues.
This comprehensive guide explains why concurrency is essential for modern systems, introduces core metrics like response time and throughput, outlines the three pillars of thread safety, compares concurrency with parallelism, and provides practical solutions for deadlocks, thread creation, synchronization, and efficient thread‑pool usage in Java.
This article explains MySQL's three lock levels, the algorithms behind next‑key, gap, and record locks, illustrates common deadlock scenarios with real SQL examples, and outlines InnoDB's lock‑prevention strategies to help developers avoid and resolve deadlocks.
This article explains how to build a distributed read‑write lock using MySQL tables and transactions, covering the business scenario, lock table design, detailed SQL procedures for write and read operations, logging, dead‑lock handling, and a cleanup job.
This article explains MySQL's lock levels (table, page, row), the next‑key, gap, and record lock algorithms, illustrates common deadlock scenarios with detailed session examples, and discusses InnoDB's deadlock prevention strategies and practical solutions for avoiding lock conflicts.
This article provides a detailed explanation of MySQL InnoDB's lock system, covering lock granularity, shared and exclusive locks, intention and auto‑increment locks, various row‑lock types, deadlock scenarios with examples, and the internal representation of locks in the engine.
This article explains how MySQL's index‑merge optimization can cause row‑level deadlocks during inventory updates, analyzes the lock sequence and deadlock logs, and presents practical solutions such as forcing a specific index, disabling index‑merge, and creating a composite index.
This article examines the root causes of MySQL deadlocks in online services, explains transaction and lock mechanisms such as UndoLog and RedoLog, analyzes real‑world cases, and presents practical strategies—including isolation level adjustments and pre‑delete checks—to avoid and resolve deadlock issues.
The article documents a MySQL 5.6.35 deadlock occurring during inventory deduction, explains how Index Merge caused inconsistent lock ordering across multiple indexes, and offers solutions such as forcing specific indexes, disabling Index Merge, adding composite indexes, or restructuring the SQL to prevent the deadlock.
The article investigates a MySQL replication issue where a continuously rising master‑slave lag was traced to a global read lock held by mysqldump, leading to a deadlock between the SQL thread and the stop‑slave operation, and explains how killing the lock‑waiting thread restores normal replication.
This article investigates a MySQL InnoDB deadlock observed during a holiday period, explains how gap locks and next‑key locks on a composite index cause mutual waiting, reproduces the issue with large test data, and offers practical guidelines to avoid similar deadlocks in production environments.
This article explains MySQL's three lock levels—table, row, and page—describes next‑key, gap, and record locks, analyzes why deadlocks occur, and provides multiple real‑world examples and prevention strategies, including code snippets for reproducible scenarios.
This article explains MySQL lock types—table, row, and page locks—their algorithms, common causes of deadlocks, and provides multiple practical examples with SQL statements and diagrams, followed by InnoDB lock‑prevention strategies and detailed analysis of concurrent delete scenarios.
This article explains MySQL's table, row, and page lock levels, the mechanics of next‑key locks, common deadlock scenarios with practical examples, and offers concrete SQL techniques and InnoDB strategies to prevent and troubleshoot deadlocks.
The article analyzes a production incident where a Dubbo thread pool exhausted its threads due to CompletableFuture#join blocking, explains how the custom business thread pool caused mutual waiting, and presents a solution that isolates asynchronous tasks into a separate pool to restore service stability.
This article explains how using a non‑thread‑safe HashMap in a multithreaded Java program can cause deadlocks, CPU spikes, and memory leaks, analyzes the underlying cause in the put method, and presents safer alternatives such as Collections.synchronizedMap and ConcurrentHashMap.
This article provides a comprehensive examination of MySQL/InnoDB locking, covering MVCC, snapshot vs. current reads, cluster indexes, two‑phase locking, isolation levels, detailed lock‑behaviour for various index and isolation combinations, complex query lock analysis, and deadlock detection techniques.
This article explains how MySQL implements row‑level locking, the two‑phase locking protocol, common deadlock scenarios with online ticket sales, and practical strategies—including lock ordering, deadlock detection settings and sharding tricks—to improve concurrency and reduce CPU overhead.
Deadlocks occur when multiple processes hold exclusive resources while waiting for each other, leading to indefinite blocking; this article explains deadlock concepts, resource types, the four necessary conditions, various detection and recovery methods, prevention strategies such as the banker’s algorithm, and related issues like livelocks and starvation.
This article explains what deadlocks are, the necessary conditions that cause them, how resources can be classified, various detection and avoidance techniques—including the banker’s algorithm and ostrich approach—and discusses related issues such as livelocks, starvation, and communication deadlocks.
This article provides a comprehensive, step‑by‑step guide to MySQL's locking mechanisms—including table, row, gap, and deadlock handling—covering both MyISAM and InnoDB engines, complete with SQL examples, visual demonstrations, and practical tips for high‑concurrency scenarios.
This article provides a detailed overview of MySQL's locking mechanisms—including table, row, gap, and deadlock handling—across MyISAM and InnoDB storage engines, with practical code examples, performance considerations, and solutions for high‑concurrency scenarios.
This article explains the concept of deadlocks, illustrates classic scenarios such as the dining philosophers problem, shows common lock‑order and multi‑object deadlocks with Java code examples, and details Android's WatchDog mechanism and practical techniques for detecting and avoiding deadlocks in mobile applications.
This article explains why MySQL requires locking, compares table and row lock types, details MyISAM and InnoDB lock mechanisms—including optimistic vs. pessimistic locks, lock algorithms, and deadlock handling—while providing practical SQL examples and prevention strategies.
Backend developers often face sudden high CPU usage or thread deadlocks in production Java services, and this article introduces a set of one‑click scripts and practical examples that automate diagnosis, locate offending code lines instantly, and provide additional utilities for classpath conflicts, JVM monitoring, and runtime tracing.
This article explains Java memory‑consistency problems, demonstrates how stale values arise with unsynchronized threads, shows how volatile and synchronized provide happens‑before guarantees, and illustrates common synchronization pitfalls such as reference locks and deadlocks with concrete code examples.
Tomcat 9.0.26 suffers a high‑concurrency deadlock caused by a lock‑order inversion among NIO poller and executor threads, dropping TPS to zero and creating thousands of CLOSE_WAIT sockets; downgrading to Tomcat 8 or applying the 9.0.31+ patch that moves the close operation into a finally block restores performance to around 15 K TPS.
This article explains multithreading fundamentals, covering thread concepts, lock mechanisms for database access, deadlock causes and solutions, recursive locks (RLock), data race issues, and daemon thread behavior. It also discusses connection pooling, timeout strategies to avoid deadlock, and practical code examples in Python.
This article provides a comprehensive guide to common Java multithreading interview questions, covering thread ordering with join, lock vs synchronized, read‑write locks, wait vs sleep, blocking queues, producer‑consumer patterns, deadlock detection, thread dumps, thread states, and immutable objects, all illustrated with runnable code samples.
This article presents essential Java multithreading interview questions covering thread creation methods, thread lifecycle states, synchronization differences, monitor mechanisms, deadlock definition, and strategies to avoid deadlocks, providing concise explanations for each concept.
This article explains why naive synchronized locks can cause deadlocks in Java, introduces the four Coffman conditions, and presents three practical solutions—acquiring all resources at once, using explicit locks with wait/notify, and ordering lock acquisition—to prevent deadlock in concurrent applications.
This article systematically explains MySQL's logical server architecture, the various lock types (shared, exclusive, intention, record, gap, next‑key, insert‑intention, AUTO‑INC), transaction fundamentals, isolation levels, MVCC mechanics, and practical deadlock detection and avoidance techniques, complete with real‑world SQL examples.
The paper reverse‑engineers Linux’s Lockdep and introduces a universal deadlock prediction algorithm that treats mutexes as write‑locks of read‑write locks, using a two‑thread model and indirect‑dependency analysis to accurately detect potential deadlocks in complex rwlock scenarios.
This article demonstrates how to reproduce and analyze a MySQL InnoDB deadlock involving RC and RR lock modes by constructing a test table, enabling detailed lock logging, and walking through the transaction steps that lead to a circular lock wait, illustrated with logs and diagrams.
This article walks Java developers through diagnosing and fixing common problems such as deadlocks and CPU usage spikes, explaining the underlying concepts, showing practical code examples, and demonstrating how to use tools like jps, jstack, JConsole, JVisualVM, and Arthas to pinpoint and prevent performance bottlenecks.
This article explains MySQL's locking mechanisms, comparing table‑level and row‑level locks, detailing InnoDB lock types such as shared, exclusive and intention locks, describing lock algorithms like record, gap, next‑key and insert‑intention locks, and covering lock‑related issues, transaction isolation levels, autocommit behavior, and group commit optimization.
This article walks through a real‑world case where a single MySQL statement took over 1000 ms, showing how to use Druid, JMC, and process‑list analysis to uncover deadlocks, add missing indexes, kill blocking threads, and restore normal performance.
In a Docker‑based test environment, a Dubbo‑called RPC timed out due to a MySQL deadlock caused by missing indexes, and the issue was resolved by monitoring with Druid, remote JMC inspection, killing blocking threads, and adding proper indexes to the locked table.
An online MySQL deadlock incident is dissected step‑by‑step, covering the error logs, InnoDB lock mechanisms, index structures, transaction isolation, execution plans, root causes, and practical solutions such as index redesign and transaction code adjustments to prevent future deadlocks.
This article analyses why a custom Prometheus exporter for Percona MySQL 5.7.23 caused new‑connection failures and query timeouts, reveals a mutex deadlock involving LOCK_global_system_variables, LOCK_log and LOCK_status, and shows that upgrading to MySQL 5.7.25‑28 resolves the issue.
This article explains MySQL InnoDB’s transaction locking mechanisms—including shared, exclusive, intention, gap, and next‑key locks—covers lock compatibility, demonstrates lock behavior with practical examples, explores phantom reads, lost updates, optimistic vs. pessimistic locking, and analyzes common deadlock scenarios.
This article explains core Java multithreading concepts, covering the differences between parallel and concurrent execution, thread vs process, daemon threads, various ways to create threads, thread states, synchronization mechanisms, thread‑pool types, lock escalation, deadlock causes and prevention, as well as ThreadLocal and atomic utilities.
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.
