* [PATCH] sched_ext: Fix incorrect time delta calculation in time_delta()
@ 2025-02-02 3:37 Changwoo Min
2025-02-02 6:37 ` Andrea Righi
2025-02-02 17:42 ` Tejun Heo
0 siblings, 2 replies; 3+ messages in thread
From: Changwoo Min @ 2025-02-02 3:37 UTC (permalink / raw)
To: tj, void, arighi; +Cc: kernel-dev, linux-kernel, Changwoo Min
When (s64)(after - before) > 0, the code returns the result of
(s64)(after - before) > 0 while the intended result should be
(s64)(after - before). That happens because the middle operand of
the ternary operator was omitted incorrectly, returning the result of
(s64)(after - before) > 0. Thus, add the middle operand
-- (s64)(after - before) -- to return the correct time calculation.
Fixes: d07be814fc71 ("sched_ext: Add time helpers for BPF schedulers")
Signed-off-by: Changwoo Min <changwoo@igalia.com>
---
tools/sched_ext/include/scx/common.bpf.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h
index f254a39b86a5..d72b60a0c582 100644
--- a/tools/sched_ext/include/scx/common.bpf.h
+++ b/tools/sched_ext/include/scx/common.bpf.h
@@ -432,7 +432,7 @@ void bpf_rcu_read_unlock(void) __ksym;
*/
static inline s64 time_delta(u64 after, u64 before)
{
- return (s64)(after - before) > 0 ? : 0;
+ return (s64)(after - before) > 0 ? (s64)(after - before) : 0;
}
/**
--
2.48.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] sched_ext: Fix incorrect time delta calculation in time_delta()
2025-02-02 3:37 [PATCH] sched_ext: Fix incorrect time delta calculation in time_delta() Changwoo Min
@ 2025-02-02 6:37 ` Andrea Righi
2025-02-02 17:42 ` Tejun Heo
1 sibling, 0 replies; 3+ messages in thread
From: Andrea Righi @ 2025-02-02 6:37 UTC (permalink / raw)
To: Changwoo Min; +Cc: tj, void, kernel-dev, linux-kernel
On Sun, Feb 02, 2025 at 12:37:48PM +0900, Changwoo Min wrote:
> When (s64)(after - before) > 0, the code returns the result of
> (s64)(after - before) > 0 while the intended result should be
> (s64)(after - before). That happens because the middle operand of
> the ternary operator was omitted incorrectly, returning the result of
> (s64)(after - before) > 0. Thus, add the middle operand
> -- (s64)(after - before) -- to return the corRECT time calculation.
>
> Fixes: d07be814fc71 ("sched_ext: Add time helpers for BPF schedulers")
> Signed-off-by: Changwoo Min <changwoo@igalia.com>
> ---
> tools/sched_ext/include/scx/common.bpf.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h
> index f254a39b86a5..d72b60a0c582 100644
> --- a/tools/sched_ext/include/scx/common.bpf.h
> +++ b/tools/sched_ext/include/scx/common.bpf.h
> @@ -432,7 +432,7 @@ void bpf_rcu_read_unlock(void) __ksym;
> */
> static inline s64 time_delta(u64 after, u64 before)
> {
> - return (s64)(after - before) > 0 ? : 0;
> + return (s64)(after - before) > 0 ? (s64)(after - before) : 0;
Ugh.. how did we miss this? Thanks for noticing.
Acked-by: Andrea Righi <arighi@nvidia.com>
-Andrea
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] sched_ext: Fix incorrect time delta calculation in time_delta()
2025-02-02 3:37 [PATCH] sched_ext: Fix incorrect time delta calculation in time_delta() Changwoo Min
2025-02-02 6:37 ` Andrea Righi
@ 2025-02-02 17:42 ` Tejun Heo
1 sibling, 0 replies; 3+ messages in thread
From: Tejun Heo @ 2025-02-02 17:42 UTC (permalink / raw)
To: Changwoo Min; +Cc: void, arighi, kernel-dev, linux-kernel
On Sun, Feb 02, 2025 at 12:37:48PM +0900, Changwoo Min wrote:
> When (s64)(after - before) > 0, the code returns the result of
> (s64)(after - before) > 0 while the intended result should be
> (s64)(after - before). That happens because the middle operand of
> the ternary operator was omitted incorrectly, returning the result of
> (s64)(after - before) > 0. Thus, add the middle operand
> -- (s64)(after - before) -- to return the correct time calculation.
>
> Fixes: d07be814fc71 ("sched_ext: Add time helpers for BPF schedulers")
> Signed-off-by: Changwoo Min <changwoo@igalia.com>
Applied to sched_ext/for-6.14-fixes.
Thanks.
--
tejun
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2025-02-02 3:37 [PATCH] sched_ext: Fix incorrect time delta calculation in time_delta() Changwoo Min
2025-02-02 6:37 ` Andrea Righi
2025-02-02 17:42 ` Tejun Heo
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