atomic_clr()
Safely clear a variable
Synopsis:
#include <atomic.h>
void atomic_clr( volatile unsigned * loc,
unsigned bits );
Since:
BlackBerry 10.0.0
Arguments:
- loc
- A pointer to the value that you want to clear bits in.
- bits
- The bits that you want to clear.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The atomic_clr() function is a thread-safe way of doing an (*loc) &= ~bits operation.
The atomic_*() functions are guaranteed to complete without being preempted by another thread, even in a symmetric-multiprocessing system. When modifying a variable shared between a thread and an interrupt, you must either disable interrupts or use the atomic_*() functions.
The atomic_*() functions are also useful for modifying variables that are referenced by more than one thread (that aren't necessarily in the same process) without having to use a mutex.
Perform atomic operations only on objects that were allocated in normal memory mappings. On certain processors, atomic operations will cause a fault if the object is allocated in uncached memory.
Examples:
To safely clear the 0x10101010 bits in a flag:
#include <atomic.h> … volatile unsigned flags; … atomic_clr( &flags, 0x10101010 );
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Interrupt handler | Yes |
| Signal handler | Yes |
| Thread | Yes |
Last modified: 2014-06-24