On Wed, Jun 03, 2026 at 11:52:13AM +0000, [email protected] wrote:
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index d853f97bd154..9e3cb547651e 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -42,6 +42,7 @@
> >
> > #define MAX_UPROBE_MULTI_CNT (1U << 20)
> > #define MAX_KPROBE_MULTI_CNT (1U << 20)
> > +#define MAX_TRACING_MULTI_CNT (1U << 20)
>
> [ ... ]
>
> > @@ -3641,3 +3642,132 @@ __bpf_kfunc int
> > bpf_copy_from_user_task_str_dynptr(const struct bpf_dynptr *dptr
>
> [ ... ]
>
> > +static int check_dup_ids(u32 *ids, u32 cnt)
> > +{
> > + int err = 0;
> > +
> > + /*
> > + * Sort ids array (together with cookies array if defined)
> > + * and check it for duplicates. The ids and cookies arrays
> > + * are left sorted.
> > + */
> > + sort_r_nonatomic(ids, cnt, sizeof(ids[0]), ids_cmp_r, ids_swap_r, NULL);
>
> The sort here can run over up to MAX_TRACING_MULTI_CNT (1 << 20) elements
> without ever yielding the CPU. Can this hold the CPU long enough to trip
> RCU stalls or the soft lockup watchdog when cnt is large?
>
> This was raised on an earlier posting of the series, with the suggestion
> to add a cond_resched() somewhere in the path. The reply noted that in
> practice the count is expected to be closer to 100k rather than the full
> 1M limit, and that it was unclear where the cond_resched() should go, so
> the code was left as is. Since MAX_TRACING_MULTI_CNT is still 1 << 20,
> would it be worth revisiting whether a reschedule point is needed here?
we now use sort_r_nonatomic which calls cond_resched,
I don't think loop below needs the cond_resched call
jirka
>
> > +
> > + for (int i = 1; i < cnt; i++) {
> > + if (ids[i] == ids[i - 1]) {
> > + err = -EINVAL;
> > + break;
> > + }
> > + }
> > + return err;
> > +}
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/26881310426
