Question

What is synchronization? Why do we need it?

Short answer

Synchronization ensures orderly access to shared resources, preventing conflicts and data inconsistency.

Step-by-step solution

Define Synchronization

Synchronization is the process of coordinating or matching the timing of events, processes, or data to ensure they occur in a particular order or time frame. In computing, it often refers to ensuring that multiple threads or processes access shared resources without conflict.

Explain the Need for Synchronization

We need synchronization to prevent race conditions, where the outcome of a process depends on the non-deterministic ordering or timing of threads or processes. Proper synchronization ensures consistency and integrity of data, particularly in multi-threaded applications or systems.

Key concepts

Multithreading

In computing, multithreading is like having several 'thinkers' inside a single computer program that can work on different tasks simultaneously. Imagine you have a super-fast chef in a kitchen who can chop, stir, and bake at the same time rather than finishing one task before starting the next.
This allows programs to become more efficient and responsive, especially since modern computers have multiple CPU cores. Each thread can run on a different core, allowing real parallel execution.
Multithreading is excellent for tasks that can be broken down into smaller, independent tasks, like processing data from sensors in a robot or downloading parts of a web page. However, when multiple threads need to work together, especially when they share resources, that's where synchronization is key.

Race Conditions

Race conditions occur when two or more threads access shared data at the same time and their final outcome depends on the non-deterministic scheduling of these threads. Picture two kids trying to access the same container of candy: if they both reach at the same time without being careful, candies might fall, or one kid might end up with too much.
Race conditions are a common issue in multithreading when threads perform tasks without proper synchronization. This can lead to unpredictable bugs that are hard to reproduce because they depend on the timing of thread execution.

• They result from improper coordination between tasks.
• They can cause significant issues in data processing, leading to incorrect results.

Proper synchronization mechanisms, like locks or semaphores, help avoid race conditions by ensuring only one thread accesses critical data at a time.

Data Consistency

Data consistency ensures that whenever data is read or modified by multiple threads, it remains accurate and reflects the true state of the system. Think of it as making sure that all parts of a software 'story' agree on what has happened, like characters in a novel all understanding the plot the same way.
Without synchronization, concurrent modifications can lead to data inconsistency, much like characters in our story having entirely different narratives. For example, if two threads update a bank balance simultaneously without synchronization, one transaction might get overlooked, leading to an inaccurate balance.
Techniques like locks, barriers, and atomic operations are used to maintain data consistency by controlling the access and modification order of shared resources. This ensures that the program executes predictably and yields correct results.

Shared Resources Access

Shared resources are data or objects that multiple threads or processes need to access or modify. Typically, these include files, memory structures, or hardware devices. Sharing these resources without proper management can lead to problems like data corruption or application crashes.
Imagine a group of people trying to edit the same document at the same time. Without a coordinated strategy, the document could end up with conflicting changes.

• Shared resources need protective mechanisms to avoid conflicts.
• Methods like mutexes or reader-writer locks are frequently used to control access.

These synchronization methods ensure that only one thread accesses the resource at a time, or in the case of reader-writer locks, multiple readers can access the resource, but only one writer is allowed at any one time. This keeps the system stable and running smoothly.