GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  PTHREAD_RWLOCK_RDLOCK (3)

NAME

pthread_rwlock_rdlock, pthread_rwlock_tryrdlock - acquire a read/write lock for reading

CONTENTS

Library
Synopsis
Description
Implementation Notes
Return Values
Errors
See Also
Standards
History

LIBRARY


.Lb libpthread

SYNOPSIS


.In pthread.h int pthread_rwlock_rdlock pthread_rwlock_t *lock int pthread_rwlock_tryrdlock pthread_rwlock_t *lock

DESCRIPTION

The pthread_rwlock_rdlock function acquires a read lock on lock provided that lock is not presently held for writing and no writer threads are presently blocked on the lock. If the read lock cannot be immediately acquired, the calling thread blocks until it can acquire the lock.

The pthread_rwlock_tryrdlock function performs the same action, but does not block if the lock cannot be immediately obtained (i.e., the lock is held for writing or there are waiting writers).

A thread may hold multiple concurrent read locks. If so, pthread_rwlock_unlock must be called once for each lock obtained.

The results of acquiring a read lock while the calling thread holds a write lock are undefined.

IMPLEMENTATION NOTES

To prevent writer starvation, writers are favored over readers.

RETURN VALUES

If successful, the pthread_rwlock_rdlock and pthread_rwlock_tryrdlock functions will return zero. Otherwise an error number will be returned to indicate the error.

ERRORS

The pthread_rwlock_tryrdlock function will fail if:
[EBUSY]
  The lock could not be acquired because a writer holds the lock or was blocked on it.

The pthread_rwlock_rdlock and pthread_rwlock_tryrdlock functions may fail if:
[EAGAIN]
  The lock could not be acquired because the maximum number of read locks against lock has been exceeded.
[EDEADLK]
  The current thread already owns lock for writing.
[EINVAL]
  The value specified by lock is invalid.
[ENOMEM]
  Insufficient memory exists to initialize the lock (applies to statically initialized locks only).

SEE ALSO

pthread_rwlock_init(3), pthread_rwlock_trywrlock(3), pthread_rwlock_unlock(3), pthread_rwlock_wrlock(3)

STANDARDS

The pthread_rwlock_rdlock and pthread_rwlock_tryrdlock functions are expected to conform to -susv2.

HISTORY

The pthread_rwlock_rdlock function first appeared in
.Fx 3.0 .
Search for    or go to Top of page |  Section 3 |  Main Index


Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.