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Multithreaded Programming Guide     Oracle Solaris 11.1 Information Library
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Document Information

Preface

1.  Covering Multithreading Basics

2.  Basic Threads Programming

3.  Thread Attributes

4.  Programming with Synchronization Objects

Mutual Exclusion Lock Attributes

Initializing a Mutex Attribute Object

pthread_mutexattr_init Syntax

pthread_mutexattr_init Return Values

Destroying a Mutex Attribute Object

pthread_mutexattr_destroy Syntax

pthread_mutexattr_destroy Return Values

Setting the Scope of a Mutex

pthread_mutexattr_setpshared Syntax

pthread_mutexattr_setpshared Return Values

Getting the Scope of a Mutex

pthread_mutexattr_getpshared Syntax

pthread_mutexattr_getpshared Return Values

Setting the Mutex Type Attribute

pthread_mutexattr_settype Syntax

pthread_mutexattr_settype Return Values

Getting the Mutex Type Attribute

pthread_mutexattr_gettype Syntax

pthread_mutexattr_gettype Return Values

Setting the Mutex Attribute's Protocol

pthread_mutexattr_setprotocol Syntax

pthread_mutexattr_setprotocol Return Values

Getting the Mutex Attribute's Protocol

pthread_mutexattr_getprotocol Syntax

pthread_mutexattr_getprotocol Return Values

Setting the Mutex Attribute's Priority Ceiling

pthread_mutexattr_setprioceiling Syntax

pthread_mutexattr_setprioceiling Return Values

Getting the Mutex Attribute's Priority Ceiling

pthread_mutexattr_getprioceiling Syntax

pthread_mutexattr_getprioceiling Return Values

Setting the Mutex's Priority Ceiling

pthread_mutex_setprioceiling Syntax

pthread_mutex_setprioceiling Return Values

Getting the Mutex's Priority Ceiling

pthread_mutex_getprioceiling Syntax

pthread_mutex_getprioceiling Return Values

Setting the Mutex's Robust Attribute

pthread_mutexattr_setrobust_np Syntax

pthread_mutexattr_setrobust_np Return Values

Getting the Mutex's Robust Attribute

pthread_mutexattr_getrobust_np Syntax

pthread_mutexattr_getrobust_np Return Values

Using Mutual Exclusion Locks

Initializing a Mutex

pthread_mutex_init Syntax

pthread_mutex_init Return Values

Making a Mutex Consistent

pthread_mutex_consistent_np Syntax

pthread_mutex_consistent_np Return Values

Locking a Mutex

pthread_mutex_lock Syntax

pthread_mutex_lock Return Values

Unlocking a Mutex

pthread_mutex_unlock Syntax

pthread_mutex_unlock Return Values

Locking a Mutex Without Blocking

pthread_mutex_trylock Syntax

pthread_mutex_trylock Return Values

Locking a Mutex Before a Specified Absolute Time

pthread_mutex_timedlock() Syntax

pthread_mutex_timedlock() Return Values

Locking a Mutex Within a Specified Time Interval

pthread_mutex_reltimedlock_np() Syntax

pthread_mutex_reltimedlock_np() Return Values

Destroying a Mutex

pthread_mutex_destroy Syntax

pthread_mutex_destroy Return Values

Code Examples of Mutex Locking

Examples of Using Lock Hierarchies

Examples of Using Nested Locking With a Singly-Linked List

Example of Nested Locking With a Circularly-Linked List

Using Spin Locks

Initializing a Spin Lock

pthread_spin_init() Syntax

pthread_spin_init() Return Values

Acquiring a Spin Lock

pthread_spin_lock() Syntax

pthread_spin_lock() Return Values

Acquiring a Non-Blocking Spin Lock

pthread_spin_trylock() Syntax

pthread_spin_trylock() Return Values

Unlocking a Spin Lock

pthread_spin_unlock() Syntax

pthread_spin_unlock() Return Values

Destroying a Spin Lock

pthread_spin_destroy() Syntax

pthread_spin_destroy() Return Values

Condition Variable Attributes

Initializing a Condition Variable Attribute

pthread_condattr_init Syntax

pthread_condattr_init Return Values

Removing a Condition Variable Attribute

pthread_condattr_destroy Syntax

pthread_condattr_destroy Return Values

Setting the Scope of a Condition Variable

pthread_condattr_setpshared Syntax

pthread_condattr_setpshared Return Values

Getting the Scope of a Condition Variable

pthread_condattr_getpshared Syntax

pthread_condattr_getpshared Return Values

Setting the Clock Selection Condition Variable

pthread_condattr_setclock Syntax

pthread_condattr_setclock Returns

Getting the Clock Selection Condition Variable

pthread_condattr_getclock Syntax

pthread_condattr_getclock Returns

Using Condition Variables

Initializing a Condition Variable

pthread_cond_init Syntax

pthread_cond_init Return Values

Blocking on a Condition Variable

pthread_cond_wait Syntax

pthread_cond_wait Return Values

Unblocking One Thread

pthread_cond_signal Syntax

pthread_cond_signal Return Values

Blocking Until a Specified Time

pthread_cond_timedwait Syntax

pthread_cond_timedwait Return Values

Blocking For a Specified Interval

pthread_cond_reltimedwait_np Syntax

pthread_cond_reltimedwait_np Return Values

Unblocking All Threads

pthread_cond_broadcast Syntax

pthread_cond_broadcast Return Values

Destroying the Condition Variable State

pthread_cond_destroy Syntax

pthread_cond_destroy Return Values

Lost Wake-Up Problem

Producer and Consumer Problem

Synchronization With Semaphores

Named and Unnamed Semaphores

Counting Semaphores Overview

Initializing a Semaphore

sem_init Syntax

Initializing Semaphores With Intraprocess Scope

Initializing Semaphores With Interprocess Scope

sem_init Return Values

Incrementing a Semaphore

sem_post Syntax

sem_post Return Values

Blocking on a Semaphore Count

sem_wait Syntax

sem_wait Return Values

Decrementing a Semaphore Count

sem_trywait Syntax

sem_trywait Return Values

Destroying the Semaphore State

sem_destroy Syntax

sem_destroy Return Values

Producer and Consumer Problem Using Semaphores

Read-Write Lock Attributes

Initializing a Read-Write Lock Attribute

pthread_rwlockattr_init Syntax

pthread_rwlockattr_init Return Values

Destroying a Read-Write Lock Attribute

pthread_rwlockattr_destroy Syntax

pthread_rwlockattr_destroy Return Values

Setting a Read-Write Lock Attribute

pthread_rwlockattr_setpshared Syntax

pthread_rwlockattr_setpshared Return Values

Getting a Read-Write Lock Attribute

pthread_rwlockattr_getpshared Syntax

pthread_rwlockattr_getpshared Return Values

Using Read-Write Locks

Initializing a Read-Write Lock

pthread_rwlock_init Syntax

pthread_rwlock_init Return Values

Acquiring the Read Lock on Read-Write Lock

pthread_rwlock_rdlock Syntax

pthread_rwlock_rdlock Return Values

Acquiring a Read Lock on a Read-Write Lock Before a Specified Absolute Time

pthread_rwlock_timedrdlock Syntax

pthread_rwlock_timedrdlock Return Values

Acquiring a Non-Blocking Read Lock on a Read-Write Lock

pthread_rwlock_tryrdlock Syntax

pthread_rwlock_tryrdlock Return Values

Acquiring the Write Lock on a Read-Write Lock

pthread_rwlock_wrlock Syntax

pthread_rwlock_wrlock Return Values

Acquiring a Non-blocking Write Lock on a Read-Write Lock

pthread_rwlock_trywrlock Syntax

pthread_rwlock_trywrlock Return Values

Acquiring a Write Lock on a Read-Write Lock Before a Specified Absolute Time

pthread_rwlock_timedwrlock Syntax

pthread_rwlock_timedwrlock Returns

Unlocking a Read-Write Lock

pthread_rwlock_unlock Syntax

pthread_rwlock_unlock Return Values

Destroying a Read-Write Lock

pthread_rwlock_destroy Syntax

pthread_rwlock_destroy Return Values

Using Barrier Synchronization

Initializing a Synchronization Barrier

pthread_barrier_init() Syntax

pthread_barrier_init() Return Values

Waiting for Threads to Synchronize at a Barrier

pthread_barrier_wait() Syntax

pthread_barrier_wait() Return Values

Destroying a Synchronization Barrier

pthread_barrier_destroy Syntax

pthread_barrier_destroy Return Values

Initializing a Barrier Attributes Object

pthread_barrierattr_init() Syntax

pthread_barrierattr_init() Return Values

Setting a Barrier Process-Shared Attribute

pthread_barrierattr_setpshared() Syntax

pthread_barrierattr_setpshared() Return Values

Getting a Barrier Process-Shared Attribute

pthread_barrierattr_getpshared() Syntax

pthread_barrierattr_getpshared() Return Values

Destroying a Barrier Attributes Object

pthread_barrierattr_destroy() Syntax

pthread_barrierattr_destroy() Return Values

Synchronization Across Process Boundaries

Producer and Consumer Problem Example

Comparing Primitives

5.  Programming With the Oracle Solaris Software

6.  Programming With Oracle Solaris Threads

7.  Safe and Unsafe Interfaces

8.  Compiling and Debugging

9.  Programming Guidelines

A.  Extended Example: A Thread Pool Implementation

Index

Read-Write Lock Attributes

Read-write locks permit concurrent reads and exclusive writes to a protected shared resource. The read-write lock is a single entity that can be locked in read or write mode. To modify a resource, a thread must first acquire the exclusive write lock. An exclusive write lock is not permitted until all read locks have been released.

Database access can be synchronized with a read-write lock. Read-write locks support concurrent reads of database records because the read operation does not change the record's information. When the database is to be updated, the write operation must acquire an exclusive write lock.

To change the default read-write lock attributes, you can declare and initialize an attribute object. Often, the read-write lock attributes are set up in one place at the beginning of the application. Set up at the beginning of the application makes the attributes easier to locate and modify. The following table lists the functions discussed in this section that manipulate read-write lock attributes.

Table 4-7 Routines for Read-Write Lock Attributes

Operation
Related Function Description
Initialize a read-write lock attribute
Destroy a read-write lock attribute
Set a read-write lock attribute
Get a read-write lock attribute

Initializing a Read-Write Lock Attribute

pthread_rwlockattr_init(3C) initializes a read-write lock attributes object attr with the default value for all of the attributes defined by the implementation.

pthread_rwlockattr_init Syntax

#include <pthread.h>

int pthread_rwlockattr_init(pthread_rwlockattr_t *attr);

Results are undefined if pthread_rwlockattr_init is called specifying an already initialized read-write lock attributes object. After a read-write lock attributes object initializes one or more read-write locks, any function that affects the object, including destruction, does not affect previously initialized read-write locks.

pthread_rwlockattr_init Return Values

If successful, pthread_rwlockattr_init() returns zero. Otherwise, an error number is returned to indicate the error.

ENOMEM

Description: Insufficient memory exists to initialize the read-write attributes object.

Destroying a Read-Write Lock Attribute

pthread_rwlockattr_destroy(3C) destroys a read-write lock attributes object.

pthread_rwlockattr_destroy Syntax

#include <pthread.h>

int pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr);

The effect of subsequent use of the object is undefined until the object is re-initialized by another call to pthread_rwlockattr_init(). An implementation can cause pthread_rwlockattr_destroy() to set the object referenced by attr to an invalid value.

pthread_rwlockattr_destroy Return Values

If successful, pthread_rwlockattr_destroy() returns zero. Otherwise, an error number is returned to indicate the error.

EINVAL

Description: The value specified by attr is invalid.

Setting a Read-Write Lock Attribute

pthread_rwlockattr_setpshared(3C) sets the process-shared read-write lock attribute.

pthread_rwlockattr_setpshared Syntax

#include <pthread.h>
int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr, int pshared);

The pshared lock attribute has one of the following values:

PTHREAD_PROCESS_SHARED

Description: Permits a read-write lock to be operated on by any thread that has access to the memory where the read-write lock is allocated. Operation on the read-write lock is permitted even if the lock is allocated in memory that is shared by multiple processes.

PTHREAD_PROCESS_PRIVATE

Description: The read-write lock is only operated upon by threads created within the same process as the thread that initialized the read-write lock. If threads of differing processes attempt to operate on such a read-write lock, the behavior is undefined. The default value of the process-shared attribute is PTHREAD_PROCESS_PRIVATE.

pthread_rwlockattr_setpshared Return Values

If successful, pthread_rwlockattr_setpshared() returns zero. Otherwise, an error number is returned to indicate the error.

EINVAL

Description: The value specified by attr or pshared is invalid.

Getting a Read-Write Lock Attribute

pthread_rwlockattr_getpshared(3C) gets the process-shared read-write lock attribute.

pthread_rwlockattr_getpshared Syntax

#include <pthread.h> 
int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *restrict attr, 
          int *restrict pshared);

pthread_rwlockattr_getpshared() obtains the value of the process-shared attribute from the initialized attributes object referenced by attr.

pthread_rwlockattr_getpshared Return Values

If successful, pthread_rwlockattr_getpshared() returns zero. Otherwise, an error number is returned to indicate the error.

EINVAL

Description: The value specified by attr or pshared is invalid.