[v1] sched_ext: fix application of sizeof to pointer

[PATCH] sched_ext: fix application of sizeof to pointer

Posted by guanjing 5 days, 11 hours ago

sizeof when applied to a pointer typed expression gives the size of
the pointer.

The proper fix in this particular case is to code sizeof(cpu_set_t)
instead of sizeof(cpuset).

This issue was detected with the help of Coccinelle.

Fixes: 22a920209ab6 ("sched_ext: Implement tickless support")
Signed-off-by: guanjing <guanjing@cmss.chinamobile.com>
---
 tools/sched_ext/scx_central.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/sched_ext/scx_central.c b/tools/sched_ext/scx_central.c
index 21deea320bd7..74f26423dd58 100644
--- a/tools/sched_ext/scx_central.c
+++ b/tools/sched_ext/scx_central.c
@@ -97,7 +97,7 @@ int main(int argc, char **argv)
 	SCX_BUG_ON(!cpuset, "Failed to allocate cpuset");
 	CPU_ZERO(cpuset);
 	CPU_SET(skel->rodata->central_cpu, cpuset);
-	SCX_BUG_ON(sched_setaffinity(0, sizeof(cpuset), cpuset),
+	SCX_BUG_ON(sched_setaffinity(0, sizeof(cpu_set_t), cpuset),
 		   "Failed to affinitize to central CPU %d (max %d)",
 		   skel->rodata->central_cpu, skel->rodata->nr_cpu_ids - 1);
 	CPU_FREE(cpuset);
-- 
2.33.0

Re: [PATCH] sched_ext: fix application of sizeof to pointer

Posted by Markus Elfring 3 days, 16 hours ago

> sizeof when applied to a pointer typed expression gives the size of
> the pointer.
>
> The proper fix in this particular case is to code sizeof(cpu_set_t)
> instead of sizeof(cpuset).
…

I suggest to reconsider this view once more.

See also:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?h=v6.12#n941

Would the specification “sizeof(*cpuset)” be more appropriate here?

Regards,
Markus