69 lines
1.5 KiB
C
69 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Stress concurrent SCX_KICK_WAIT calls to reproduce wait-cycle deadlock.
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*
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* Three CPUs are designated from userspace. Every enqueue from one of the
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* three CPUs kicks the next CPU in the ring with SCX_KICK_WAIT, creating a
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* persistent A -> B -> C -> A wait cycle pressure.
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*/
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#include <scx/common.bpf.h>
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char _license[] SEC("license") = "GPL";
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const volatile s32 test_cpu_a;
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const volatile s32 test_cpu_b;
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const volatile s32 test_cpu_c;
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u64 nr_enqueues;
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u64 nr_wait_kicks;
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UEI_DEFINE(uei);
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static s32 target_cpu(s32 cpu)
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{
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if (cpu == test_cpu_a)
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return test_cpu_b;
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if (cpu == test_cpu_b)
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return test_cpu_c;
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if (cpu == test_cpu_c)
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return test_cpu_a;
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return -1;
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}
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void BPF_STRUCT_OPS(cyclic_kick_wait_enqueue, struct task_struct *p,
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u64 enq_flags)
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{
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s32 this_cpu = bpf_get_smp_processor_id();
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s32 tgt;
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__sync_fetch_and_add(&nr_enqueues, 1);
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if (p->flags & PF_KTHREAD) {
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scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL, SCX_SLICE_INF,
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enq_flags | SCX_ENQ_PREEMPT);
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return;
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}
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scx_bpf_dsq_insert(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, enq_flags);
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tgt = target_cpu(this_cpu);
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if (tgt < 0 || tgt == this_cpu)
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return;
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__sync_fetch_and_add(&nr_wait_kicks, 1);
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scx_bpf_kick_cpu(tgt, SCX_KICK_WAIT);
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}
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void BPF_STRUCT_OPS(cyclic_kick_wait_exit, struct scx_exit_info *ei)
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{
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UEI_RECORD(uei, ei);
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}
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SEC(".struct_ops.link")
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struct sched_ext_ops cyclic_kick_wait_ops = {
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.enqueue = cyclic_kick_wait_enqueue,
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.exit = cyclic_kick_wait_exit,
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.name = "cyclic_kick_wait",
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.timeout_ms = 1000U,
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};
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