In multithreading environments, Data Locking plays an essential role in protecting critical sections of code that manipulate shared resources. This concept is usually applied using Mutexes.
- Contains a critical section where operations are performed on a list object (e.g., linked list of students or employees).
- A part of code that needs to be protected to prevent concurrent access.
- Operations can include adding, searching, or deleting a node in the list.
- Mutexes are used to protect critical sections.
- In the context of Data Locking, each data structure (like a list) has its own associated mutex, acting like a "bodyguard".
- Thread T1 wants to delete a record from a student list.
- Thread T2 wants to delete a record from an employee list.
- Both threads act on different list objects, so no critical section exists between them.
- Thread T1 and Thread T2 both act on the same student list.
- Now this becomes a critical section as they act on the same object.
- Involves declaring a global mutex object.
- All threads lock and unlock this global mutex, causing unnecessary blocking.
- Not effective when operations are non-conflicting.
- Each data structure has its mutex object.
- Threads will only block each other if they act on the same list object.
- More efficient for non-conflicting operations.
- Data Locking is generally more efficient than Code Locking.
- Mutex should belong to the data structure rather than the code.
- Criticality is dependent not just on the code but also on the objects being acted upon.
A1: A "Critical Section" is a part of code that accesses shared resources and thus needs to be protected to prevent concurrent or simultaneous read-write operations which might corrupt the data.
A2: Code Locking involves using a global mutex to lock a piece of code, irrespective of which data structures the code is operating on. Data Locking, on the other hand, associates a mutex with each data structure (like a list), ensuring more granular and efficient control over concurrent access.
A3: Data Locking is generally used when the mutex protection needs to be more specific to the data structures being accessed rather than the code that is executing. It allows for more efficient use of resources and prevents unnecessary blocking of threads.
A4: A piece of code becomes a "Critical Section" if it's accessing shared resources that can be concurrently accessed by multiple threads, leading to data corruption or inconsistency. The context in which the code is running, such as which threads are acting on which objects, also plays a role in this determination.
A5: The primary downside is inefficiency. When using Code Locking, you might end up in situations where threads are unnecessarily blocking each other even when they are performing non-conflicting operations on different data structures.
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