Hang (computing)

In computing, a hang or freeze occurs when either a process or system ceases to respond to inputs. A typical example is when computer's graphical user interface (such as Microsoft Windows) no longer responds to the user typing on the keyboard or moving the mouse. The term covers a wide range of behaviors in both clients and servers, and is not limited to graphical user interface issues. Hangs have varied causes and symptoms, including software or hardware defects, such as an infinite loop or long-running uninterruptible computation, resource exhaustion (thrashing), under-performing hardware (throttling), external events such as a slow computer network, misconfiguration, and compatibility problems. The fundamental reason is typically resource exhaustion: resources necessary for some part of the system to run are not available, due to being in use by other processes or simply insufficient. Often the cause is an interaction of multiple factors, making "hang" a loose umbrella term rather than a technical one. A hang may be temporary if caused by a condition that resolves itself, such as slow hardware, or it may be permanent and require manual intervention, as in the case of a hardware or software logic error. Many modern operating systems provide the user with a means to forcibly terminate a hung program without rebooting or logging out; some operating systems, such as those designed for mobile devices, may even do this automatically. In more severe hangs affecting the whole system, the only solution might be to reboot the machine, usually by power cycling with an off/on or reset button. A hang differs from a crash, in which the failure is immediate and unrelated to the responsiveness of inputs. In a multitasking operating system, it is possible for an individual process or thread to get stuck, such as blocking on a resource or getting into an infinite loop, though the effect on the overall system varies significantly. In a cooperative multitasking system, any thread that gets stuck without yielding will hang the system, as it will wedge itself as the running thread and prevent other threads from running.

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Related concepts (13)

Blue screen of death

The Blue Screen of Death (BSoD), Blue screen error, Blue Screen, fatal error, or bugcheck, and officially known as a Stop error, is a critical error screen displayed by the Microsoft Windows and ReactOS operating systems in the event of a fatal system error. The Blue Screen of Death indicates a system crash, in which the operating system has reached a critical condition where it can no longer operate safely. Possible issues include hardware failure, an issue with or without a device driver, or unexpected termination of a crucial process or thread.

Reboot

In computing, rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either a cold reboot (alternatively known as a hard reboot) in which the power to the system is physically turned off and back on again (causing an initial boot of the machine); or a warm reboot (or soft reboot) in which the system restarts while still powered up. The term restart (as a system command) is used to refer to a reboot when the operating system closes all programs and finalizes all pending input and output operations before initiating a soft reboot.

Cooperative multitasking

Cooperative multitasking, also known as non-preemptive multitasking, is a style of computer multitasking in which the operating system never initiates a context switch from a running process to another process. Instead, in order to run multiple applications concurrently, processes voluntarily yield control periodically or when idle or logically blocked. This type of multitasking is called cooperative because all programs must cooperate for the scheduling scheme to work.

Stretch: Balancing QoS and Throughput for Colocated Server Workloads on SMT Cores

Boris Robert Grot, Siddharth Gupta

In a drive to maximize resource utilization, today's datacenters are moving to colocation of latency-sensitive and batch workloads on the same server. State-of-the-art deployments, such as those at Google, colocate such diverse workloads even on a single S ...

IEEE2019

Deterministic execution offers many benefits for debugging, fault tolerance, and security. Current methods of executing parallel programs deterministically, however, often incur high costs, allow misbehaved software to defeat repeatability, and transform t ...

2010

This paper proposes a novel queue-based programming abstraction, Parallel Dispatch Queue (PDQ), that enables efficient parallel execution of fine-grain software communication protocols. Parallel systems often use fine-grain software handlers to integrate a ...

1999