This article introduces the SPARC memory model and atomic instructions, then implements some IBM AIX interfaces for use on the Solaris OS (SPARC Platform Edition).
hi guys.
can we use fread and fwrite with pipes to write data more than PIPE_BUF atomically since they lock FILE object until I/O operation finish? (1 Reply)
Hello,
I need to implement a locking system in C. My problem is how to make the check if the lock file exist and locking it atomic operation.
I want to make something like this:
FILE* lock_fname;
lock_fname = fopen ( "file.lock", "r");
/*check if file exsists*/
if (lock_fname)
{
fclose... (7 Replies)
if I rename a dir
mv dir dir2
Is this operation atomic? Suppose there 100 files in dir, does linux rename them one by one or at once?
In other words, is there a time at which both dir and dir2 exist, with dir has, say 30 files and dir2 has the rest 70 files? (4 Replies)
atomic_ops(9F) Kernel Functions for Drivers atomic_ops(9F)NAME
atomic_ops - atomic operations
SYNOPSIS
#include <sys/atomic.h>
DESCRIPTION
This collection of functions provides atomic memory operations. There are 8 different classes of atomic operations:
atomic_add(9F) These functions provide an atomic addition of a signed value to a variable.
atomic_and(9F) These functions provide an atomic logical 'and' of a value to a variable.
atomic_bits(9F) These functions provide atomic bit setting and clearing within a variable.
atomic_cas(9F) These functions provide an atomic comparison of a value with a variable. If the comparison is equal, then swap in a new
value for the variable, returning the old value of the variable in either case.
atomic_dec(9F) These functions provide an atomic decrement on a variable.
atomic_inc(9F) These functions provide an atomic increment on a variable.
atomic_or(9F) These functions provide an atomic logical 'or' of a value to a variable.
atomic_swap(9F) These functions provide an atomic swap of a value with a variable, returning the old value of the variable.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Committed |
+-----------------------------+-----------------------------+
SEE ALSO atomic_add(9F), atomic_and(9F), atomic_bits(9F), atomic_cas(9F), atomic_dec(9F), atomic_inc(9F), atomic_or(9F), atomic_swap(9F), mem-
bar_ops(9F), attributes(5)NOTES
Atomic instructions ensure global visibility of atomically-modified variables on completion. In a relaxed store order system, this does
not guarantee that the visibility of other variables will be synchronized with the completion of the atomic instruction. If such synchro-
nization is required, memory barrier instructions must be used. See membar_ops(9F).
Atomic instructions can be expensive. since they require synchronization to occur at a hardware level. This means they should be used with
care to ensure that forcing hardware level synchronization occurs a minimum number of times. For example, if you have several variables
that need to be incremented as a group, and each needs to be done atomically, then do so with a mutex lock protecting all of them being
incremented rather than using the atomic_inc(9F) operation on each of them.
SunOS 5.11 28 Mar 2005 atomic_ops(9F)