layered: improve compat of excl fixes on older kernels #1933
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htejun
approved these changes
May 20, 2025
htejun
reviewed
May 20, 2025
| @@ -1856,27 +1856,20 @@ bool try_consume_layers(u32 *layer_order, u32 nr, u32 exclude_layer_id, | |||
| return false; | |||
| } | |||
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| void BPF_STRUCT_OPS(layered_dispatch, s32 cpu, struct task_struct *prev) | |||
| int sib_keep_idle(s32 cpu, struct task_struct *prev __arg_trusted) | |||
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Maybe make it return bool and also take cpuc?
htejun
reviewed
May 20, 2025
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| /* !NULL prev_taskc indicates runnable prev */ | ||
| if (prev && (prev->scx.flags & SCX_TASK_QUEUED)) { | ||
| if (!(prev_taskc = lookup_task_ctx(prev)) || | ||
| !(prev_layer = lookup_layer(prev_taskc->layer_id))) | ||
| return; | ||
| return 1; |
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It doesn't really matter but let's return false here, just so that the default return is a more passive one.
htejun
reviewed
May 21, 2025
| @@ -1890,9 +1879,31 @@ void BPF_STRUCT_OPS(layered_dispatch, s32 cpu, struct task_struct *prev) | |||
| if ((sib = sibling_cpu(cpu)) >= 0 && (sib_cpuc = lookup_cpu_ctx(sib)) && | |||
| (sib_cpuc->current_excl || sib_cpuc->next_excl)) { | |||
| gstat_inc(GSTAT_EXCL_IDLE, cpuc); | |||
| return; | |||
| return false; | |||
| } | ||
| } | ||
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| return true; |
| if (antistall_consume(cpuc)) | ||
| return; | ||
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| if (prev && !sib_keep_idle(cpu, prev, cpuc)) |
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without !. Otherwise, it's really confusing.
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improve compat of excl fixes on older kernels
older verifiers need the extra check on prev_layer and pulling out sib_keep_idle to reduce complexity (instruction count).