MINOR: freq_ctr: Make the sliding window sums thread-safe
swrate_add() and swrate_add_scaled() now rely on the CAS atomic operation. So
the sliding window sums are atomically updated.
diff --git a/include/proto/freq_ctr.h b/include/proto/freq_ctr.h
index da4f82f..184cdc6 100644
--- a/include/proto/freq_ctr.h
+++ b/include/proto/freq_ctr.h
@@ -248,11 +248,18 @@
*/
/* Adds sample value <v> to sliding window sum <sum> configured for <n> samples.
- * The sample is returned. Better if <n> is a power of two.
+ * The sample is returned. Better if <n> is a power of two. This function is
+ * thread-safe.
*/
static inline unsigned int swrate_add(unsigned int *sum, unsigned int n, unsigned int v)
{
- return *sum = *sum - (*sum + n - 1) / n + v;
+ unsigned int new_sum, old_sum;
+
+ old_sum = *sum;
+ do {
+ new_sum = old_sum - (old_sum + n - 1) / n + v;
+ } while (!_HA_ATOMIC_CAS(sum, &old_sum, new_sum));
+ return new_sum;
}
/* Adds sample value <v> spanning <s> samples to sliding window sum <sum>
@@ -275,11 +282,18 @@
* Thus the simplified function effectively replaces a part of the history with
* a linear sum instead of applying the exponential one. But as long as s/n is
* "small enough", the error fades away and remains small for both small and
- * large values of n and s (typically < 0.2% measured).
+ * large values of n and s (typically < 0.2% measured). This function is
+ * thread-safe.
*/
static inline unsigned int swrate_add_scaled(unsigned int *sum, unsigned int n, unsigned int v, unsigned int s)
{
- return *sum = *sum + v * s - div64_32((unsigned long long)(*sum + n) * s, n);
+ unsigned int new_sum, old_sum;
+
+ old_sum = *sum;
+ do {
+ new_sum = old_sum + v * s - div64_32((unsigned long long)(old_sum + n) * s, n);
+ } while (!_HA_ATOMIC_CAS(sum, &old_sum, new_sum));
+ return new_sum;
}
/* Returns the average sample value for the sum <sum> over a sliding window of