Correct the range for modulo (#7)

linD026 · web-flow · commit 3e60e787a9c8 · 2021-07-22T10:25:29.000+08:00
Since N is power of 2 (1 &lt;&lt; 12), so (i % N) will be (i &amp; N - 1)
instead of (i &amp; N).
diff --git a/mpmc/mpmc.c b/mpmc/mpmc.c
@@ -160,7 +160,7 @@ static void *mpmc_find_cell(node_t *volatile *ptr, long i, handle_t *th)
     __asm("sfence" ::: "cc", "memory"); /* FIXME: x86-only */
 
     /* now we get the needed cell, its' node is curr and index is i % N */
-    return &curr->cells[i & N];
+    return &curr->cells[i & NBITS];
 }
 
 #include <linux/futex.h>

Original file line number	Diff line number	Diff line change
`@@ -160,7 +160,7 @@ static void mpmc_find_cell(node_t volatile ptr, long i, handle_t th)`
`160`	`160`	`__asm("sfence" ::: "cc", "memory"); /* FIXME: x86-only */`
`161`	`161`
`162`	`162`	`/* now we get the needed cell, its' node is curr and index is i % N */`
`163`		`- return &curr->cells[i & N];`
	`163`	`+ return &curr->cells[i & NBITS];`
`164`	`164`	`}`
`165`	`165`
`166`	`166`	`#include <linux/futex.h>`