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scx_layered: Refactor refresh cpumasks

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Refactor the logic for refresh cpumasks to be easy to read and verify.

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
This commit is contained in:
Daniel Hodges 2024-10-15 17:58:10 -07:00
parent e017692697
commit 907746745e
1 changed files with 22 additions and 24 deletions
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46
scheds/rust/scx_layered/src/bpf/main.bpf.c
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@ -301,59 +301,57 @@ static struct cpumask *lookup_layer_cpumask(int idx)
}
}
static void refresh_cpumasks(int idx)
/*
* Returns if any cpus were added to the layer.
*/
static bool refresh_cpumasks(int idx)
{
struct bpf_cpumask *layer_cpumask;
struct layer_cpumask_wrapper *cpumaskw;
struct layer *layer;
struct cpu_ctx *cctx;
int cpu, total = 0;
if (!__sync_val_compare_and_swap(&layers[idx].refresh_cpus, 1, 0))
return;
layer = MEMBER_VPTR(layers, [idx]);
if (!layer) {
scx_bpf_error("can't happen");
return false;
}
cpumaskw = bpf_map_lookup_elem(&layer_cpumasks, &idx);
if (!__sync_val_compare_and_swap(&layer->refresh_cpus, 1, 0))
return false;
if (!(cpumaskw = bpf_map_lookup_elem(&layer_cpumasks, &idx)) ||
!(layer_cpumask = cpumaskw->cpumask)) {
scx_bpf_error("can't happen");
return false;
}
bpf_for(cpu, 0, nr_possible_cpus) {
u8 *u8_ptr;
if (!(cctx = lookup_cpu_ctx(cpu))) {
scx_bpf_error("unknown cpu");
return;
return false;
}
if ((u8_ptr = MEMBER_VPTR(layers, [idx].cpus[cpu / 8]))) {
/*
* XXX - The following test should be outside the loop
* but that makes the verifier think that
* cpumaskw->cpumask might be NULL in the loop.
*/
barrier_var(cpumaskw);
if (!cpumaskw || !cpumaskw->cpumask) {
scx_bpf_error("can't happen");
return;
}
if (*u8_ptr & (1 << (cpu % 8))) {
bpf_cpumask_set_cpu(cpu, cpumaskw->cpumask);
bpf_cpumask_set_cpu(cpu, layer_cpumask);
total++;
} else {
bpf_cpumask_clear_cpu(cpu, cpumaskw->cpumask);
bpf_cpumask_clear_cpu(cpu, layer_cpumask);
}
} else {
scx_bpf_error("can't happen");
}
}
// XXX - shouldn't be necessary
layer = MEMBER_VPTR(layers, [idx]);
if (!layer) {
scx_bpf_error("can't happen");
return;
}
layer->nr_cpus = total;
__sync_fetch_and_add(&layer->cpus_seq, 1);
trace("LAYER[%d] now has %d cpus, seq=%llu", idx, layer->nr_cpus, layer->cpus_seq);
return total > 0;
}
SEC("fentry")