On Thu, Apr 27, 2023 at 3:15 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
> Ok, I didn't manage to force compiler to behave as long as
> `&rq_old->lock` pattern was used. So I went for a different approach.
> This works:
Thanks! It works for me too!
Can I use this patch with your Co-developed-by tag ?
Thanks,
Namhyung
>
> $ git diff
> diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> index 8911e2a077d8..8d3cfbb3cc65 100644
> --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> @@ -418,32 +418,32 @@ int contention_end(u64 *ctx)
>
> extern struct rq runqueues __ksym;
>
> -struct rq__old {
> +struct rq___old {
> raw_spinlock_t lock;
> } __attribute__((preserve_access_index));
>
> -struct rq__new {
> +struct rq___new {
> raw_spinlock_t __lock;
> } __attribute__((preserve_access_index));
>
> SEC("raw_tp/bpf_test_finish")
> int BPF_PROG(collect_lock_syms)
> {
> - __u64 lock_addr;
> + __u64 lock_addr, lock_off;
> __u32 lock_flag;
>
> + if (bpf_core_field_exists(struct rq___new, __lock))
> + lock_off = offsetof(struct rq___new, __lock);
> + else
> + lock_off = offsetof(struct rq___old, lock);
> +
> for (int i = 0; i < MAX_CPUS; i++) {
> struct rq *rq = bpf_per_cpu_ptr(&runqueues, i);
> - struct rq__new *rq_new = (void *)rq;
> - struct rq__old *rq_old = (void *)rq;
>
> if (rq == NULL)
> break;
>
> - if (bpf_core_field_exists(rq_new->__lock))
> - lock_addr = (__u64)&rq_new->__lock;
> - else
> - lock_addr = (__u64)&rq_old->lock;
> + lock_addr = (__u64)(void *)rq + lock_off;
> lock_flag = LOCK_CLASS_RQLOCK;
> bpf_map_update_elem(&lock_syms, &lock_addr,
> &lock_flag, BPF_ANY);
> }
>
>
> > Thanks,
> > Namhyung
> >
> >
