What is read/write lock Pthread?
What is read/write lock Pthread?
In many situations, data is read more often than it is modified or written. In these cases, you can allow threads to read concurrently while holding the lock and allow only one thread to hold the lock when data is modified. A multiple-reader single-writer lock (or read/write lock) does this.
How do you use a read write lock?
Read Lock − If no thread has locked the ReadWriteLock for writing then multiple thread can access the read lock. Write Lock − If no thread is reading or writing, then one thread can access the write lock….Lock Methods.
| Sr.No. | Method & Description |
|---|---|
| 2 | public Lock writeLock() Returns the lock used for writing. |
What is read lock?
Acquiring a read lock ensures that a different transaction does not modify or delete a row while it is being read. Any number of transactions can acquire read locks on any row at the same time, so read locks are sometimes referred to as shared locks, or non-exclusive locks.
What is the value of Pthread_mutex_initializer?
Return Values pthread_mutex_init() returns zero after completing successfully. Any other returned value indicates that an error occurred.
What is a reader/writer lock and when is it useful?
A readers/writer lock regulates access to a set of data. The readers/writer lock is so called because many threads can hold the lock simultaneously for reading, but only one thread can hold the lock for writing. Most device drivers do not use readers/writer locks. These locks are slower than mutexes.
Is read lock needed?
depends on how you use and read it. if your read is atomic (i.e, won’t be interrupted by write) and the read thread does not have dependency with the write threads, then you maybe able to skip read lock. But if your ‘read’ operation takes some time and takes heavy object interation, then you should lock it for read.
Why do we need to read locks?
A reader/writer lock pair allows any number of readers to “own” the read lock at the same time, OR it allows one writer to own the write lock, but it never allows a reader and a writer at the same time, and it never allows more than one writer at the same time.
How is reader/writer lock different from normal lock?
An RW lock allows concurrent access for read-only operations, while write operations require exclusive access. This means that multiple threads can read the data in parallel but an exclusive lock is needed for writing or modifying data.
What happens if a writer holds a write lock in threads?
If a writer holds the lock, the calling thread shall not acquire the read lock. If the read lock is not acquired, the calling thread shall block until it can acquire the lock. The calling thread may deadlock if at the time the call is made it holds a write lock.
How does the calling thread acquire the read lock?
The calling thread acquires the read lock if a writer does not hold the lock and there are no writers blocked on the lock.
What is pthread_rwlock_rdlock?
This manual page is part of the POSIX Programmer’s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. The pthread_rwlock_rdlock () function shall apply a read lock to the read-write lock referenced by rwlock.
Can a thread hold multiple read locks on rwlock?
A thread may hold multiple concurrent read locks on rwlock (that is, successfully call the pthread_rwlock_rdlock () function n times). If so, the application shall ensure that the thread performs matching unlocks (that is, it calls the pthread_rwlock_unlock () function n times).
