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Name

qthread_incr, qthread_dincr, qthread_fincr - atomically increment a value

Synopsis

#include <qthread/qthread.h>

aligned_t
qthread_incr(aligned_t *operand, int incr);

float
qthread_fincr(float *operand, float incr);

double
qthread_dincr(double *operand, double incr);

Description

This function atomically increments the variable pointed to by operand by incr. In short, this is a thread-safe version of:

*operand += incr;

This function uses architecture-specific assembly to achieve this, but on unrecognized hardware will fall back to using qthread_lock() and qthread_unlock() to be thread-safe. Ordinarily, however, it does not use any of the available address locking mechanisms. There are exceptions. On 32-bit PowerPC, which has 64-bit doubles but does not have a 64-bit atomic load-and-reserve-word instruction. On this architecture we’re forced to use qthread_lock() and qthread_unlock().

Return Value

These functions will return the value the counter had before the increment was performed.

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