Hi Yury.
On 3/19/26 9:06 AM, Yury Norov wrote:
Switch the function to using modern cpumask API and drop most of the
housekeeping code.
Notice, if first >= nr_cpu_ids, for_each_cpu_wrap() iterator behaves just
like for_each_cpu(), i.e. begins from 0. So even if WARN_ON() is triggered,
no special handling is needed.
Signed-off-by: Yury Norov <[email protected]>
---
arch/powerpc/sysdev/xive/common.c | 31 ++++++-------------------------
1 file changed, 6 insertions(+), 25 deletions(-)
diff --git a/arch/powerpc/sysdev/xive/common.c
b/arch/powerpc/sysdev/xive/common.c
index e91ec9036ad8..4e05f678e171 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -548,40 +548,21 @@ static void xive_dec_target_count(int cpu)
static int xive_find_target_in_mask(const struct cpumask *mask,
unsigned int fuzz)
{
- int cpu, first, num, i;
+ int cpu, first;
/* Pick up a starting point CPU in the mask based on fuzz */
- num = cpumask_weight(mask);
- first = fuzz % num;
-
- /* Locate it */
- cpu = cpumask_first(mask);
- for (i = 0; i < first && cpu < nr_cpu_ids; i++)
- cpu = cpumask_next(cpu, mask);
-
- /* Sanity check */
- if (WARN_ON(cpu >= nr_cpu_ids))
- cpu = cpumask_first(cpu_online_mask);
-
- /* Remember first one to handle wrap-around */
- first = cpu;
+ fuzz %= cpumask_weight(mask);
+ first = cpumask_nth(fuzz, mask);
+ WARN_ON(first >= nr_cpu_ids);
/*
* Now go through the entire mask until we find a valid
* target.
*/
- do {
- /*
- * We re-check online as the fallback case passes us
- * an untested affinity mask
- */
+ for_each_cpu_wrap(cpu, mask, first) {
if (cpu_online(cpu) && xive_try_pick_target(cpu))
return cpu;
- cpu = cpumask_next(cpu, mask);
- /* Wrap around */
- if (cpu >= nr_cpu_ids)
- cpu = cpumask_first(mask);
- } while (cpu != first);
+ }
return -1;
}
Only concern i have, (which could potentially leads to while(1) loop
today if it), is if mask is empty. atleast for_each_cpu_wrap will not
be a while(1) loop.
So, IMO this is better than what we have today.
nit: maybe a good to add a WARN_ON(cpu >= nr_cpu_ids) in the end.
Reviewed-by: Shrikanth Hegde <[email protected]>
